ͻ
           Seattle Treatment Education Project  (STEP)                    
                   DRUG INTERACTION INFORMATION                           
                          December, 1994                                  
   (206) 329-4857   *   127 Broadway E. Ste 200   *   Seattle, WA 98102   
ͼ

As HIV research continues to evolve, people with HIV infection are
better equipped to prevent and fight related manifestations and
infections. As a result however, it is becoming more complicated
for individuals and their health care providers to plan and administer
therapies, hoping to avoid adverse drug interactions. As the
number of medications an individual uses increases, so does the
possibility of drug interactions.

This booklet, written in collaboration with a licensed pharmacist
and reviewed by an infectious disease specialist, outlines some
of the interactions of common agents used in HIV and HIV-related
manifestations. It is designed to be used as a guide in conjunction
with advice from your healthcare provider and other sources.
With many of the newer agents, not all possible adverse drug
reactions are known, therefore this booklet serves only as a guide.

NOTE: For further distribution information, please refer to the end
of this file

STEP is asking a $2.50 donation for their beautifully typeset
and formatted document, Drug Interaction Information.  Please
see the form at the end of this document for ordering info.

----------------------------------------------------------------------

[Electronic version distributed from Seattle, by
Seattle AIDS Information BBS (206) 323-4420 (8-N-1)
FS Node 169:206/188, Voice (8 am - 8 pm) (206) 329-8617]
Distribution of this information must be at no charge for
the reader.


                   DRUG INTERACTION INFORMATION


Medication:        Treatment for:           Interacts with:
===============================================================================

Acyclovir          Herpes Simplex           Probenecid -- Decreased clearance
(Zivorax)          type 1 and 2             of acyclovir, possibly leading to
                   Varicella zoster         increased incidence of side
                   virus (shingles)         effects.

------------------------------------------------------------------------------

Alfa               KS,                      AZT -- Increased risk of bone
Interferon         hepatitis                marrow toxicity. Careful monitor-
                                            ing of the WBC is essential.

------------------------------------------------------------------------------

Amphotericin B     Cryptococcal             Antineoplastic agents -- This
(Fungizon)         meningitis               combination may enhance the
                                            potential for renal toxicity,
                                            bronchospasm and hyotension
                                            (low blood pressure) and should
                                            only be used with great caution.

                                            AZT -- May increase the risk of
                                            bone marrow toxicity especially
                                            anemia. Monitor CBC frequently.

                                            Corticosteroids -- May increase
                                            the risk of hypo-kalemia (de-
                                            creased potassium levels) which
                                            can lead to cardiac dysfunction.
                                            If these drugs must be used
                                            concomitantly, monitor serum
                                            electrolytees and cardiac
                                            function closely.

                                            Flucytosine (5-FC) -- This com-
                                            bination is sometimes used in
                                            treating cryptococcal meningitis
                                            because of possible synergistic
                                            effects. This combination how-
                                            ever, may impair the excretion
                                            of flucytosine, therefore
                                            increasing the toxicity.

                                            Imidazoles (ketoconazole, flu-
                                            conazole, clotrimazole, etc) --
                                            In test tube and animal studies,
                                            the use of these drugs with
                                            amphotericin B induced the
                                            development of fungal resistance
                                            to amphotericin B.

                                            Pentamidine (IV) -- This combin-
                                            ation may enhance the potential
                                            for renal toxicity. Intensive
                                            monitoring of renal function is
                                            recommended.

------------------------------------------------------------------------------

Atovaquone         Pneumocystis             Food -- take with meals.
(Mepron)           pneumonia
                                            Phenytoin (Dilantin) -- Mepron
                                            causes decreased absorption of
                                            Phenytoin. Monitor Dilantin
                                            levels and adjust dosage
                                            as necessary.

------------------------------------------------------------------------------

Azithromycin       MAC                      Antacids -- Antacids decrease
(Zithromax)        cryptosporidiosis        the absorption rate of
                   toxoplasmosis            azithromycin. Therefore
                                            azithromycin should be taken
                                            at least two hours after
                                            antiacids

                                            ddI -- ddI contains a large
                                            amount of antacid which will
                                            decrease the absorption of
                                            azithromycin. Take at least
                                            two hours after ddI.

                                            Food -- Food interferes with
                                            the absorption of azithromycin,
                                            take at least one hour before
                                            or two hours after meals.

------------------------------------------------------------------------------

AZT                antiviral                Alfa Interferon -- increased
Retrovir           AIDS dementia            risk of bone marrow toxicity.
Zidovudine)        complex                  Monitor CBC frequently.

                                            Amphotericin B -- Increased risk
                                            of bone marrow toxicity. Monitor
                                            CBC frequently.

                                            Dapsone -- may increase the risk
                                            of bone marrow toxicity. Monitor
                                            CBC frequently.

                                            Flucytosine -- may increase the
                                            risk of bone marrow toxicity.
                                            Monitor CBC frequently.

                                            Ganciclovir -- Both drugs can
                                            cause granulocytopenia. Also,
                                            possible decreased antiviral
                                            action with both drugs. Use
                                            this combination with caution.

                                            Methadone -- Methadone may
                                            cause either increased or
                                            decreased phenytoin levels.
                                            Monitor phenytoin levels
                                            closely.

                                            Phenytoin (Dilantin) -- AZT may
                                            cause either increased or
                                            decreased phenytoin levels.
                                            Monitor phenytoin levels
                                            closely.

------------------------------------------------------------------------------

AZT                antiviral                Pyrimethamine -- Pyrimethamine
Retrovir           AIDS dementia            leads to decreased clearance
Zidovudine)        complex                  of AZT which could lead to
                                            increased risk of bone marrow
                                            toxicity. Monitor CBC
                                            frequently.

                                            TMP-SMX (e.g. septra, bactim)
                                            When TMP-SMX is used in high
                                            dosees (such as the treatment
                                            of PCP) there is an increased
                                            risk of developing neutropenia.
                                            Monitor CBC closely.

------------------------------------------------------------------------------

Carbamazepine      Peripheral               Acetamenophen -- Tagretol can
(Tegretol)         neuropathy               cause decreased acetamenophen
                                            effectiveness due to decreased
                                            absorption.

                                            Bone marrow suppressants --
                                            Use with caution when taking
                                            AZT, gancyclovir or other
                                            bone marrow suppressants.

                                            Cimeetidine -- Increased
                                            tegretol levels may result
                                            from this combination.
                                            Monitor closely.

                                            Coumadin and other anticoag-
                                            ulants -- This combination can
                                            cause increased blood clotting
                                            times leading to increased
                                            risk of bleeding.

                                            Doxycycline -- Decrease in
                                            doxycycline levels may
                                            be seen.

                                            Erythromycin -- May cause
                                            increased tegretol levels.
                                            Monitor closely.

                                            Haloperidol (Haldol) --
                                            Therapeutic effects and blood
                                            levels of Haldol may be
                                            decreased due to Tegretol.
                                            Therapeutic blood levels
                                            should be monitored for
                                            effectiveness.

                                            Isoniazid (INH) -- This
                                            combination may lead to
                                            increased (toxic) tegretol
                                            levels. Monitor closely.

                                            Lithium -- There's an increased
                                            risk of neurotoxic (nerves)
                                            side effects with this
                                            combination. Use with
                                            great care.

                                            Oral Contraceptives -- This
                                            combination may lead to
                                            increased bleeding and
                                            decreased effectiveness of
                                            the oral contraceptive.

                                            Phenobarbitol -- Decreases
                                            tegretol levels.

                                            Phenytoin (Dilantin) -- This
                                            combination decreases both the
                                            dilantin levels and tegretol
                                            levels.

                                            Theophyline -- Decreased
                                            theophyline levels may result
                                            from this combination.
                                            Monitor for optimal dosage.

------------------------------------------------------------------------------

Cimetidine         antacid                  Dapsone -- Cimetidine greatly
(Tagamet)          immunomodulator          decreases the absorption of
                                            dapsone, therefore take AT
                                            LEAST two hours apart.

                                            ddI -- Cimetidine may increase
                                            the absorption of ddI, possibly
                                            increasing the risk of toxicity.
                                            Take at least two hours apart.

                                            Ketoconazole -- Cimetidine
                                            greatly increases the absorption
                                            of ketoconazole, take at least
                                            two hours apart.

                                            Quinolon antibiotics (Cipro,
                                            Noroxin, Floxin) -- Cimetidinee
                                            reduces the absorption of
                                            these drugs, take at least
                                            two hours apart.

------------------------------------------------------------------------------
Ciprofloxacin      antibiotic               Antacids -- Antacids decrease
(Cipro)                                     the absorption of ciprofloxacin.
                                            Take at least two hours apart.

                                            Caffeine -- Cipro causes
                                            decreased clearance of caffeine,
                                            which may exaggerate or prolong
                                            the effects of caffeine.

                                            ddI -- ddI interferes with the
                                            absorption of ciprofloxacin.
                                            Take at least two hours apart.

                                            Theophylline -- Cipro causes
                                            decreased clearance of
                                            theophylline. Monitor
                                            theophylline levels closely.

                                            Zinc -- Zinc interferes with
                                            the absorption of ciprofloxacin.
                                            Take at least two hours apart.

------------------------------------------------------------------------------

Clarithromycin     MAC                      Carbamazepine (Tegretol) --
(Biaxin)                                    Clarithromycin increases the
                                            concentration of carbamazpine.
                                            Monitor carbamazepine levels.

                                            Theophylline -- Clarithromycin
                                            may increase serum concentration
                                            of theophylline; monitor
                                            theophylline levels.

------------------------------------------------------------------------------

Clindamycin        PCP                      Kaolin pectin -- Kaolin may
(Cleocin)          toxoplasmosis            decrease the absorption of
                                            clindamycin. Take at least
                                            two hours apart.

------------------------------------------------------------------------------

Cycloserine        tuberculosis             Alcohol -- Alcohol increases the
(Seromycin)                                 risk of epileptic episodes. Do
                                            not drink alcohol while taking
                                            this drug.

                                            Isoniazid -- The combination may
                                            increase the central nervous
                                            systems effects. Use with
                                            caution.

                                            Phenytoin (Dilantin) --
                                            Cycloserine causees increased
                                            risk of phenytoin toxicity.
                                            Monitor phenytoin levels and
                                            adjust dosage as necessary.

------------------------------------------------------------------------------

Dapsone            PCP                      Antacids -- Antacids cause
                                            decreased dapsone absorption.
                                            Take dapsone at least two
                                            hours before antiacids.

                                            Cimetidine -- Cimetidine causes
                                            decreased dapsone absorption.
                                            Take dapsonee at least two
                                            hours before cimetidine.

                                            Coumadin -- This combination can
                                            cause increased blood clotting
                                            times leading to increased
                                            risk of bleeding.

                                            ddC -- Potential for increased
                                            risk of peripheral neuropathy.

                                            ddI -- ddI causes decreased
                                            dapsone absorption. Take dapsone
                                            at least two hours before ddI.
                                            Also slight increased risk of
                                            peripheral neuropathy.

                                            Primaquine -- Increased hemolysis
                                            with G-6-PD deficiency. Test for
                                            G-6-PD deficiency prior to
                                            using this combination.

                                            Probenecid -- Decreased clearance
                                            of dapsone lad to increased
                                            dapsone levels, potentially
                                            causing increased side effects.

                                            Pyrimethamine -- Both drugs are
                                            folic acid antagonists, which may
                                            increase the likelihood of
                                            hematologic reactions, and may
                                            cause granulocytosis. Monitor
                                            CBC frequently.

                                            Rifampin -- Rifampin lowers
                                            dapsone levels 7 to 10 fold by
                                            accelerating plasma clearance.
                                            May need to use increased
                                            dapsone dose or use alternative
                                            form of PCP prophylaxis.

                                            Trimethoprim -- increased levels
                                            of both drugs, therefore
                                            increasing the risk of side
                                            effects. May need to decrease
                                            dosage of trimethoprim if
                                            anemia develops.

------------------------------------------------------------------------------

ddC                antiviral                Amphotericin B -- interferes
(Hivid)                                     with the renal clearance of ddC
                                            thereby raising systemic
                                            exposure. Monitor renal
                                            function.

                                            Dapsone -- Increased risk
                                            of neuropathy.

                                            ddI -- increased risk of
                                            peripheral neuropathy and
                                            pancreatitis. Do not
                                            combine these drugs.

                                            Foscarnet -- Foscarnet
                                            interferes with the renal
                                            clearance of ddC, thereby
                                            raising systemic exposure.
                                            Monitor renal function.

                                            Isoniazid -- Increased risk
                                            of peripheral neuropathy.

                                            Metronidazole -- increased
                                            risk of pripheral neuropathy.

                                            Paromomycin -- Paromomycin
                                            interferes with the renal
                                            clearance of ddC and thereby
                                            raises systemic exposure.
                                            Monitor renal function.

                                            Pentamidine (IV) -- increased
                                            risk of pancreatitis.

                                            Phenytoin (Dilantin) --
                                            increased risk of peripheral
                                            neuropathy.

                                            Ribavirin -- increased risk of
                                            peripheral neuropathy.

                                            Rifampin -- increased risk of
                                            pancreatitis.

                                            Vincristine -- increased risk of
                                            peripheral neuropathy.

------------------------------------------------------------------------------

ddI                antiviral                Alcohol -- Increases the risk of
(Videx)                                     pancreatitis. Do not drink
                                            alcohol while using this drug.

                                            Dapsone -- ddI interferes with
                                            the absorption of dapsone, take
                                            dapsone at least two hours
                                            before ddI.

                                            ddC -- Increased risk of
                                            pancreatitis and peripheral
                                            neuropathy. Do NOT combine
                                            these drugs.

                                            Food -- Food reduces the
                                            absorption of ddI by 50%. Take
                                            AT LEAST 1 hour before or two
                                            hours after eating.

                                            Isoniazid -- Increased risk of
                                            peripheral neuropathy.

                                            Ketoconazole -- ddI interferes with
                                            the absorption of ketoconazole.
                                            Take at least 2 hours before ddI.

                                            Metronidazole -- increased risk
                                            of peripheral neuropathy.

                                            Pentamidine (IV) -- Increased
                                            risk of pancreatitis. Discontinue
                                            ddI while on IV pentamadine.

                                            Quinolones -- ddI causes decreased
                                            abosorption of the quinolones. Take
                                            at least two hours before ddI.

                                            Ranitidine -- The bioavailability
                                            of ddI may be increased while
                                            that of ranitidine may be
                                            decreased.

                                            Ribavirin -- Increased risk of
                                            peripheral neuropathy.

                                            Tetracycline -- ddI causes
                                            decreased absorption of
                                            tetracycline. Take tetracycline
                                            at least 2 hours before ddI.


------------------------------------------------------------------------------

Fluconazole        fungal                   Cimetidine -- cimetidine causes
(Diflucan)         infections               decreased levels of fluconazole
                                            which can reduce the antifungal
                                            effects of fluconazole.

                                            Coumadin -- This combination
                                            can cause increased blood
                                            clotting times leading to
                                            increased risk of bleeding.

                                            Cyclosporine -- Fluconazole can
                                            cause increased cyclosporine
                                            levels, which could increease
                                            the risk of side effects.

                                            Hydrochlorothiazide -- Hydro-
                                            chlorothiazide causes increased
                                            levels of fluconazole due to
                                            decrease in renal clearance.

                                            Phenytoin (Dilantin) -- Flucona-
                                            zole causes increased levels of
                                            phenytoin. Monitor levels and
                                            adjust phenytoin dose if needed.

                                            Rifampin -- Rifampin causes
                                            decreased levels of fluconazole
                                            which can reduce th latter's
                                            effectiveness, may need to
                                            increase fluconazole dose.

                                            Sulfonylureas -- Fluconazole can
                                            caused increased levels of sulfo-
                                            nylureas. Monitor blood glucose
                                            and adjust sulfonylurea dose
                                            if needed.

------------------------------------------------------------------------------

Flucytosine        cryptococcal             Amphotericin B -- May increase
(SFC, Ancobon)     meningitis               toxicity. Monitor flucytosine
                                            levels weekly and CBC
                                            frequently.

                                            Antacids -- Antacids may
                                            decrease the absorption of
                                            flucytosine. Take antacids
                                            at least two hours prior
                                            to flucytosine.

                                            Cytosine -- Cytosine may
                                            inactivate the antifungal
                                            activity of flucytosine.

                                            Ganciclovir -- increased
                                            hematoxicity. Monitor CBC
                                            frequently.

------------------------------------------------------------------------------

Foscarnet          CMV                      Amphotericin B -- increased
(Foscavir)                                  kidney toxicity. Monitor BUN
                                            and serum creatinine three
                                            times a week.

                                            AZT -- May result in increased
                                            risk of anemia. Monitor CBC
                                            frequently.

                                            Paromomycin -- Increased kidney
                                            toxicity. Monitor BUN and
                                            serum creatinine three times
                                            a week.

                                            Pentamidine (IV) -- Increased
                                            incidence of hypocalcemia
                                            (low calcium levels) and kidney
                                            toxicity. If this combination
                                            cannot be avoided, monitor BUN
                                            and serum cratinine three
                                            times a week.


------------------------------------------------------------------------------

Ganciclovir        CMV                      Amphotericin B -- Increased
(DHPG,                                      risk of hematological
Cytovene)                                   toxicity. Amphotericin B
                                            decreases the renal clearance
                                            of ganciclovir. Use this
                                            combination with caution and
                                            monitor closely for anemia
                                            and neutropenia.

                                            AZT -- Increased granulocyto-
                                            penia, possible decreased
                                            antiviral action of both
                                            drugs. Use this combination
                                            with caution.

                                            Dapsone -- Dapsone may
                                            decrease renal clearance of
                                            ganciclovir, causing increased
                                            risk for pancreatitis. Monitor
                                            serum amylase and triglyceride
                                            levels closely.

                                            Flucytosine -- Flucytosine may
                                            decrease the renal clearance
                                            of ganciclovir, leading to
                                            increased toxicity. Monitor
                                            CBC frequently.

                                            Imipenem -- increased frequency
                                            of seizures.

                                            Pentamidine (IV) -- IV Pentami-
                                            dine may decrease renal
                                            clearance of ganciclovir,
                                            causing increased toxicity.

                                            Probenecid -- Probenecid may
                                            decreas the renal clearance of
                                            ganciclovir, causing increased
                                            toxicity.

                                            TMP/SMX -- The combination
                                            may have additive toxicity due
                                            to decreased renal clearance.

------------------------------------------------------------------------------

Isoniazid          Tuberculosis             Acetamenophen -- INH causes
(INH)                                       decreased acetamenophen
                                            metabolism, thereby
                                            increasing the effect
                                            of the latter.

                                            Alcohol -- Chronic use may
                                            increase isoniazid-related
                                            hepatitis.

                                            Antacids -- Antacids containing
                                            aluminum salts may decrease
                                            the absorption of isoniazid.
                                            Take isoniazid one to two
                                            hours prior to antacids.

                                            Anticoagulants -- Antigoagulant
                                            activity may be increased.

                                            Benzodiazepines -- INH may
                                            inhibit metabolism of benzodi-
                                            azepines thereby increasing
                                            activity of the latter.

                                            Carbamazepine (Tegretol) --
                                            INH causes decreased metabolism
                                            of carbamazepine, therefore
                                            increasing risk of liver
                                            toxicity. Monitor
                                            carbamazepine levels.

                                            Corticosteroids -- Cortico-
                                            steroids may cause increased
                                            isoniazid metabolism, leading
                                            to decreased effectiveness of
                                            INH (limited data available).

                                            Clycloserine -- Increased
                                            central nervous system toxicity.
                                            Use this combination with
                                            extreme caution.

                                            Ketoconazole -- INH can cause
                                            deeecreased serum concentrations
                                            of ketoconazole, leading to
                                            decreased antifungal efficacy.
                                            Also, Ketoconazol may cause
                                            decreased absorption of
                                            isoniazid.

                                            Meperidine -- May cause low
                                            blood pressure or central
                                            nervous system depression.
                                            Monitor blood pressure.

                                            Phenytoin (Dilantin) -- INH
                                            causes increased phenytoin
                                            toxicity due to decreased
                                            metabolism. Monitor levels and
                                            adjust dose accordingly.

                                            Rifampin -- Increased risk of
                                            liver toxicity. Monitor liver
                                            functions closely.

                                            Sufonylureas -- May cause
                                            hyperglycemia (high blood
                                            sugar). Monitor levels and
                                            adjust dose accordingly.

                                            Theophylline -- INH causes
                                            increased theophylline levels.
                                            Monitor levels and adjust
                                            dose accordingly.

------------------------------------------------------------------------------

Itraconazole       fungal                   Alcohol -- Alcohol use increases
(Sporanox)         infections               the risk of developing liver
                                            toxicity.

                                            Antacids -- Antacids act to
                                            decrease the amount of acid
                                            present in the stomach which
                                            will inhibit the absorption of
                                            itraconazole. Itraconazole must
                                            be taken at least two hours
                                            prior to antiacids.

                                            Cimetidine (and other H2
                                            antagonists) -- Decreased levels
                                            of itraconazole may result from
                                            this combination.

                                            Coumadin -- This combination can
                                            cause increased blood clotting
                                            times leading to increased risk
                                            of bleeding.

                                            ddI -- ddI contains a large
                                            amount of antacid which will
                                            interfeere with the absorption
                                            of Itraconazole. Itraconazole
                                            should be taken at least two
                                            hours apart from ddI.

                                            Food -- Take with meals.

                                            Isoniazid (INH) -- Decreased
                                            itraconazole levels may result
                                            from this combination.

                                            Phenytoin (Dylantin) -- Both
                                            drug levels in this combination
                                            need to be monitored.
                                            Decreased levels of itraconazole
                                            may occur.

                                            Rifampin -- Itraconazole dosage
                                            may need to be increased due
                                            to this combination.

                                            Sucralfate (Carafate) --
                                            Sucralfate decreases the
                                            bioavailability of
                                            intraconazole. Take at least
                                            two hours after taking
                                            itraconazole.

                                            Terfenadine (Seldane) -- Do NOT
                                            take these two drugs together.

                                            Theophylline -- This combination
                                            can decrease the activity of
                                            thophylline leading to a
                                            decrease in pulmonary function.
                                            Monitor theophylline levels
                                            and adjust dosage as needed.

------------------------------------------------------------------------------

Ketoconazole       fungal                   Alcohol -- Alcohol use increases
(Nizoral)          infections               the risk of developing liver
                                            toxicity.

                                            Anabolic steroids -- May
                                            increase the risk of liver
                                            toxicity.

                                            Antacids -- Antacids act to
                                            decrease the amount of acid
                                            present in the stomach which
                                            will inhibit the absorption of
                                            ketoconazole. Ketoconazole must
                                            be taken at least two hours
                                            prior to antacids.

                                            Anticoagulants -- This
                                            combination may increase the
                                            effects of the anticoagulants,
                                            therefore their dosage may
                                            need to be adjusted.

                                            Contraceptives (oral) -- This
                                            combination may increase the
                                            risk of devloping liver
                                            toxicity.

                                            Cimetidine -- Cimetidine
                                            decreases the amount of acid in
                                            the stomach which will decrease
                                            the absorption of ketoconazole.
                                            Ketoconazole must bee taken at
                                            least two hours prior to
                                            Cimetidine.

                                            Corticosteroids -- Ketoconazole
                                            may increase the effects and
                                            toxicity of some corticosteroids
                                            due to reduced clearance.

                                            Cyclosporine -- Ketoconazole
                                            increases the plasma
                                            concentration of cyclosporine
                                            which may increase the risk
                                            of kidney toxicity.

                                            ddI -- ddI contains a large
                                            amount of antiacid which will
                                            interfere with the absorption
                                            of Ketoconazole. Ketoconazole
                                            should be taken at least two
                                            hours apart from ddI.

                                            Erythromycin -- This combination
                                            may increase the risk of
                                            liver toxicity.

                                            Isoniazid -- INH significantly
                                            decreases serum concentration
                                            of ketoconazole. Therefore,
                                            higher doses of the anti-fungal
                                            may be needed to be taken in
                                            order to be effective.

                                            Phenytoin (Dilantin) -- This
                                            combination can alter the
                                            metabolism of one or both drugs,
                                            levels should be monitored.

                                            Ranitidine -- Ranitidine
                                            decreases the absorption of
                                            ketoconazole due to higher
                                            gastric pH. Take Ranitidine
                                            at least two hours after
                                            the ketoconazole.

                                            Rifampin -- Can significantly
                                            decrease the serum concentration
                                            of either drug, resulting in
                                            decreased effectivness. May need
                                            to increase dosages.

                                            Sulcrafate (Carafate) --
                                            Sulcrafate decreases the bio-
                                            availability of ketoconazole.
                                            Take at least two hours after
                                            taking ketoconazole.

                                            Terfenadine (Seldan) --
                                            Ketoconazole inhibits thee
                                            metabolism of terfenadine which
                                            causes an increased serum
                                            concentration and delayed
                                            elimination. This can lead to
                                            life-threatening ventricular
                                            arrhythmias. Do not use this
                                            combination.

                                            Theophylline -- This combination
                                            can decrease the activity of
                                            theophylline leading to
                                            deteoriation of pulmonary
                                            function. Monitor theophylline
                                            levels and adjust dosage.

------------------------------------------------------------------------------

Leucovorin                                  Anticonvulsants -- Large doses
                                            of leucovorin may counteract
                                            the anti-convulsant effect.

------------------------------------------------------------------------------

Metronidazole      parasitic                Alcohol -- Metronidazole
(Flagyl)           infections of            interferes with the oxidation
                   the G.I. tract           of alcohol which may result in
                                            abdominal cramps, nausea,
                                            vomiting, headache or flushing.

                                            Anticoagulants -- Metronidazole
                                            increases the effect of the
                                            anticoagulants. The dosage of
                                            the anticoagulant may need to
                                            be adjusted.

                                            Cimetidine -- Cimetidine
                                            interferes with the liver's
                                            ability to break down metroni-
                                            dazol, causing increased amounts
                                            of drug in the blood. Metroni-
                                            dazole dose may need to be
                                            reduced if toxicity occurs.

                                            Disulfiram (Antabuse) -- May
                                            result in confusion and
                                            psychotic reactions.

                                            Phenobarbital -- Phenobarbital
                                            increases the rate at which
                                            metronidazole is broken down,
                                            therefore reducing the amount
                                            of metronidazole in the blood.

                                            Phenytoin (Dylantin) -- Metroni-
                                            dazole can increase the blood
                                            levels of phenytoin causing
                                            increased pharmacologic effects.
                                            Monitor and adjust dose if
                                            needed.

                                            Capreomycin, Ethanbutil,
                                            Cytarabine, Isoniazid, Lithium
                                            Mexiletine, Viscristine,
                                            Pyridoxine (vitamin B6),
                                            long-term, high dose -- ALL
                                            may increase nervous system
                                            toxicity.

------------------------------------------------------------------------------

Mexiletine         experimental             Antacids -- Antacids decrease
(Mexitil)          treatment of             the clearance of mexiletine
                   peripheral               through the kidneys, therefore
                   neuropathy               increasing its effects.

                                            Cimetidine -- Cimetidine may
                                            either increase or decrease
                                            mexiletine levels.

                                            Urinary alkalinizers -- Urinary
                                            alkalinizers may decrease the
                                            clearance of mexiletine, leading
                                            to increased risk of side
                                            effects.

------------------------------------------------------------------------------

Paromomycin        cryptosporidiosis        Methotrexate -- Paromomycin
(Humatin)          and other G.I            causes decreased absorption
                   parasitic                of methotrexate, leading to
                   infections               decreased effectiveness
                                            of the latter.

                                            Vancomycin -- Increased
                                            kidney toxicity.

------------------------------------------------------------------------------

Pentamidine        PCP                      Amphotericin B -- increased
(IV)                                        kidney toxicity.

                                            Capreomycin -- Increased
                                            kidney toxicity.

                                            ddC -- increased risk of
                                            pancreatitis.

                                            ddI -- Increased risk of
                                            pancreatitis. Discontinue ddI
                                            while receiving IV pentamidine.

                                            Foscarnet -- Increased kidney
                                            toxicity.

                                            Paromomycin -- Increased kidney
                                            toxicity.

------------------------------------------------------------------------------

Phenytoin          seizures                 Acetamenophen -- Dilantin causes
(Dylantin)                                  a decreased effect of acetameno-
                                            phen and increased risk of
                                            liver toxicity.

                                            Alcohol (acute use) -- Alcohol
                                            used acutely leads to decreased
                                            phenytoin metabolism, and hence
                                            increased effects. Monitor
                                            phenytoin level and adjust
                                            dosage accordingly.

                                            Alcohol (chronic use) -- Chronic
                                            use of alcohol leads to
                                            increased metabolism of
                                            phenytoin, and hence decreased
                                            effectiveness.

                                            Anticoagulants -- Anticoagulants
                                            cause increase phenytoin
                                            activity, increasing the risk of
                                            toxicity of dilantin.

                                            Antihistamines -- Antihistamines
                                            cause increased phenytoin levels
                                            leading to increased pharmaco-
                                            logical effects of dilantin.
                                            Monitor phenytoin level and
                                            adjust dose as needed.

                                            AZT -- AZT can cause either
                                            increased or decreased phenytoin
                                            level. Monitor phenytoin level.

                                            Cimetidine -- Cimetidine
                                            inhibits metabolism of phenytoin
                                            leading to increased pharma-
                                            cological and toxic effects of
                                            the latter. Monitor phenytoin
                                            level and adjust dosage if
                                            necessary.

                                            Corticosteroids -- Dilantin
                                            causes decreased effects of the
                                            steroids due to increased
                                            metabolism.

                                            Diazepam -- Diazepam may
                                            increase phenytoin effects
                                            but data is conflicting.

                                            Fluconazole -- Fluconazole
                                            inhibits phenytoin metabolism,
                                            leading to increased phenytoin
                                            effects. Monitor phenytoin
                                            level and adjust dose as
                                            necessary.

                                            Folic acid -- Folic acid causes
                                            decreased phenytoin activity,
                                            leading to decreased effective-
                                            ness. Monitor phenytoin level
                                            and adjust dosage accordingly.

                                            Isoniazid -- INH inhibits
                                            phenytoin metabolism, leading
                                            to increased phenytoin effects.
                                            Monitor phenytoin level.

                                            Metronidazole -- Metronidazole
                                            inhibits phenytoin metabolism,
                                            leading to increased phenytoin
                                            effects. Monitor phenytoin
                                            level.

                                            Omeprazole -- Serum phenytoin
                                            leveels may be increased,
                                            leading to an increase in its
                                            effect. Monitor phenytoin level.

                                            Pridoxine (Vitamin B-6) --
                                            Vitamin B6 can cause a decreased
                                            effect of phenytoin.

                                            Rifampin -- Rifampin causes
                                            increased metabolism of
                                            phenytoin, leading to a
                                            decreased phenytoin effects.

                                            Sucralfate (Carafate) Sucralfate
                                            causes decreased absorption of
                                            phenytoin, which may lead to a
                                            deecreased anticonvulsant effect
                                            of phenytoin. Monitor phenytoin
                                            level and adjust dosage
                                            accordingly.

                                            TMP/SMX -- TMP/SMX inhibits
                                            metabolism of phenytoin,
                                            therefore increasing the
                                            effects of the latter.

                                            Tube feedings -- tube feedings
                                            may interfere with the
                                            absorption of phenytoin. Space
                                            two hours away from feedings.

------------------------------------------------------------------------------

Prednisone         corticosteroid           Alfa interferon -- Prednisone
                                            may inhibit the antiviral
                                            activity of alfa interferon.

                                            Amphotericin B -- The combin-
                                            ation causes an increased risk
                                            of potassium depletion.

                                            Aspirin -- Prednisone causes
                                            decreased effectiveness of
                                            aspirin and increased risk of
                                            gastrointestinal upset and
                                            bleeding.

                                            Phenobarbital -- Phenobarbital
                                            causes increased excretion of
                                            prednisone, leading to
                                            decreased effectiveness of
                                            prednisone.

                                            Phenytoin (Dilantin) --
                                            Phenytoin causes increased
                                            excretion of prednisone, leading
                                            to decreased effect of the
                                            latter.

                                            Rifampin -- Rifampin causes
                                            decreased effectiveness of
                                            prednisone. Avoid combination
                                            or increase dose of prednisone.

------------------------------------------------------------------------------

Primaquine         PCP                      Dapsone -- The combination
                                            can lead to increased hemolysis
                                            with G-6-PD deficiency. Test for
                                            deficiency before initiating
                                            therapy.

------------------------------------------------------------------------------

Pyrimethamine      toxoplasmosis            Antacids -- Antacids cause
(Daraprim)                                  decreased pyrimethamine
                                            absorption.

                                            AZT -- Increased risk of bone
                                            marrow suppression. Monitor
                                            CBC closely.

                                            Dapsone -- May cause
                                            agranulocytosis.

                                            Kaolin -- Kaolin may decrease
                                            absorption of pyrimethamine.

                                            Methotrexate -- Increased bone
                                            marrow suppression and increased
                                            risk of folic acid deficiency.

                                            TMP-SMX -- May cause megalo-
                                            blastic anemia. Use together in
                                            low dosages and monitor serum
                                            iron.

------------------------------------------------------------------------------

Rifabutin          MAC                      The drug interactions for
(Mycobutin)        prophylaxis              rifubatin are not yet known,
                                            however all drugs which interact
                                            with rifampin (see next) should
                                            be used with caution as similar
                                            interactions may occur.

------------------------------------------------------------------------------

Rifampin           tuberculosis             Anticoagulants -- increased
(Rifadin)                                   hypothrombinemia, leading to
                                            increased risk of bleeding.

                                            Barbiturates -- Rifampin causes
                                            decreased effect of barbit-
                                            urates. May require increasing
                                            barbiturate dosage.

                                            Benzodiazepines -- Rifampin may
                                            cause possible decreased benzo-
                                            diazepine effect. May require
                                            increased benzodiazepine dosage.

                                            Chloramphenicol -- Rifampin
                                            causes decreased effect of
                                            chloramphenicol. May require
                                            increased chloramphenicol
                                            dosage.

                                            Clofazimine -- Clofazimine
                                            causes reduced rifampin effect.

                                            Contraceptives, oral -- Rifampin
                                            causes reduced effectiveness
                                            of the contraceptives.

                                            Corticosteroids -- Rifampin
                                            causes a decreased effect of
                                            the corticosteroids. May require
                                            increased dosagee of the latter.

                                            Cyclosporine -- Rifampin causes
                                            a decreased effect of
                                            cyclosporine. May require
                                            increased cyclosporine dosage.

                                            Dapsone -- Rifampin causes a
                                            decreased dapsone effect. May
                                            require increased dosage of
                                            dapsone.

                                            Diflucan (Fluconazole) -- Leads
                                            to decreased levels of Diflucan.

                                            Digoxin -- Serum concentrations
                                            of digoxin may be decreased by
                                            rifampin. May require increased
                                            Digoxin dosage.

                                            Food -- Food interferes with the
                                            absorption of rifampin, so take
                                            on an empty stomach.

                                            Isoniazid -- The combination may
                                            increase the risk of liver
                                            toxicity. If changes in liver
                                            function tests occur, consider
                                            discontinuing one of the drugs.

                                            Ketaconazole -- Decreased
                                            effect of both drugs. This
                                            combination should not be used
                                            unless absolutely necessar.
                                            Increased dosages may be
                                            required.

                                            Methadone -- Rifampin may
                                            decrease the effectiveness of
                                            methadone, leading to withdrawal
                                            symptoms. May need to increase
                                            the dosage of methadone as
                                            much as 50 percent.

                                            Mexiletine -- Rifampin may
                                            decrease the effectiveness of
                                            mexiletine. May require
                                            increased dosage of thee
                                            latter.

                                            Phenytoin (Dilantin) --
                                            Rifampin causes a decreased
                                            phenytoin effect. Monitor
                                            phenytoin level and adjust
                                            dose if necessary.

                                            Trimethoprim -- Rifampin may
                                            decrease trimethoprim level.
                                            May require increased
                                            trimethoprim dosage.


------------------------------------------------------------------------------

Trimethoprim-      PCP                      Anticoagulants -- This
sulfomethoxazole                            combination may prolong the
(Septra, Bactrim,                           target prothrombin time.
TMP-SMX)                                    Monitor coagulation tests
                                            and adjust dosage as
                                            necessary.

                                            Cyclosporine -- TMP/SMX may
                                            cause a decreased effect of
                                            cyclosporine and an increased
                                            risk of kidney toxicity.

                                            Methotrexate -- May cause
                                            increased risk of bone marrow
                                            toxicity.

                                            Phenytoin (Dilantin) --
                                            Clearance of phenytoin by the
                                            liver may be decreased which
                                            could lead to increased
                                            toxicity. Monitor phenytoin
                                            level.

------------------------------------------------------------------------------

Vancomycin                                  Amphotericin B -- May increase
(Vancocin)                                  the risk of kidney toxicity.
                                            Monitor closely.

                                            Paromomycin -- May increase the
                                            risk of kidney toxicity. Monitor
                                            closely.

------------------------------------------------------------------------------

This drug interaction booklet has been prepared,
edited and revised by:

J. Mark Bray, RN
Seattle Treatment Education Project

Joel Gibson, MS
Retrovirus Lab
University of Washington

Laury McKean, RN, BSN

Lori Panther, MD
University of Washington AIDS Clinic

Freddie Toniolo, R.Ph
Fred Meyer Pharmacy

Printing courtesy of SAFECO Corporation and its employees.

Other contributions may have been made by GLAXO and Pfizer.

(C) 1994 -- Seattle Treatment Education Project

---------------------------------------------------------------------------

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