April 2000 May NUMBER EIGHT
      DRUG INTERACTIONS


    Many HIV and other drugs are broken down in the body by the same p450 liver pathways: If two drugs arrive at the liver at the same time, only one can enter, the other may be delayed. This type of interaction can cause an increase or decrease of drug levels in the blood and affect how quickly the drugs arrive at their target.

    The following table lists potentially significant drug-drug interactions. This selective, basic guide has been culled from several sources. Read the package insert for each drug you take carefully and ask your doctor about potential interactions with other types of medications, nutritional supplements, vitamins, and food. Bring all pills or meds you take with you to your doctor to ask about interactions.

    For more information on drug-drug interactions see: http://HIV.medscape.com/medscape/HIV/druginteractions/index.cfm.
    KEY: X = don't use: contraindicated ! = serious interaction = interacts = increases blood levels of bolded drug = decreases blood levels of bolded drug = bolded drug increases levels of = bolded drug decreases levels of

    AZT
    X d4T
    ! bone-marrow drugs (eg., ganciclovir, chemotherapies, antineoplastics).
    fluconazole, methadone, valproic acid.
    Ongoing use of Tylenol.

    3TC
    ! ddC

    Combivir (see AZT, 3TC).

    ddI
    X ddC, tetracyclines.
    ! pentamidine, ethambutol, ganciclovir. Avoid neuropathy causing drugs.
    Methadone, food.
    antineoplastics, alcohol. Must not be taken at same time as: quinolones, Dapsone, Rescriptor, Crixivan, Nizoral.

    ddC
    X ddI.
    ! pentamidine, 3TC. Avoid other neuropathy-causing drugs (eg., dapsone, isoniazid, cloramphenicol, ampho-B, antineoplastics, Antabuse).

    d4T
    X AZT
    Methadone.
    Avoid neuropathy-causing drugs.

    Ziagen
    X alcohol
    Consider monitoring methadone.

    Viramune
    ! Avoid Bactrim/Septra for first 4-6 weeks of Viramune; ketoconazole, rifampin, methadone (dose adjustment required).
    rifabutin
    clarithromycin, Crixivan, Norvir, Fortovase, may decrease Methadone, Viagra, birth control pills (estradiol).
    Fluconazole increases risk of rash. Many other drugs may interact with Viramune. See package insert.

    Rescriptor
    X alprazolam, cisapride, H-2 blockers, proton pump inhibitors, midazolam, triazolam, astemizole, terfenadine, rifampin, simvastatin, lovastatin, ergot drugs.
    ! Rifabutin (not recommended), amphetamines, clarithromycin. Monitor anticonvulsants.
    Viracept, Preveon, carbamazepine, MKC-442, phenobarbitol, phenytoin.
    Crixivan, Norvir, Fortovase; may increase estradiol, Viagra, dapsone, warfarin, quinidine.
    Many other drugs may interact with Rescriptor. Monitor anticonvulsants. See package insert.

    Sustiva
    X rifabutin (dose increase required), avoid clarithromycin, birth control (use alternative methods). Monitor warfarin, anticonvulsants. Methadone (consider increased dosage). astemizole, terfenidine, cisapride, midazolam, triazolam, ergot derivatives.
    rifampin
    Viracept
    Crixivan, Agenerase, may decrease Viagra.
    Sustiva may cause an initial false-positive reading on the CediaDau urine test.

    PROTEASE DRUGS: Avoid the following: simvastatin, lovastatin, rifampin, rifabutin, Nizoral, astemizole, terfenadine, cisapride, midazolam, trazolam and ergot drugs.

    Fortovase
    X clarithromycin, Rescriptor, Crixivan, Nizoral, Viracept, Norvir, grapefruit juice.
    rifabutin.
    Sustiva, Viramune, dexamethasone.
    Viagra, clarithromycin, may significantly increase tamoxifen.
    Many other drugs may interact with Fortovase. Check package insert.

    Norvir
    X Amiodarone, astemizole, bepridil, bupoprion, cisapride, clozapine, pimozide, clorazepate, estazolam, flurazepam, zolpidem, diazepine, flecainide, encainide, propafenone, quinidine, piroxicam, propoxyphene.
    ! Birth control pills (use barrier methods), Viagra. A long list of drugs. Check package insert. Dose reduction required with Nizoral, rifabutin. Watch rifampin for liver toxicity. Monitor methadone.
    Rescriptor.
    clarithromycin (dose adjustment needed), desipramine, theophylline, Sustiva, Norvir, Agenerase, Crixivan, Viracept, Fortovase.
    Methadone, Bactrim/Septra.
    Possible interactions with antidepressants such as Prozac.

    Crixivan
    St. John’s Wort.
    ! rifabutin (dose reduction required).

    Rescriptor, Nizoral, Viracept.
    Sustiva, Viramune, MKC-442, food, fluconazole.

     
    HIV-Related Drugs with Overlapping Toxicities
    Bone Marrow Suppression
    cidofovir, cotrimoxazole, cytotoxicchemotherapy, dapsone, flucytosine, ganciclovir, hydroxyurea, interferon-alpha, primaquine, pyrimethamine, ribavirin, sulfadiazine, trimetrexate, zidovudine.

    Peripheral Neuropathy
    didanosine, isoniazid, stavudine, zalcitabine.

    Pancreatitis
    cotrimoxazole, didanosine, lamivudine (children), pentamidine, ritonavir, hydroxyurea.

    Nephrotoxicity (kidney damage)
    adefovir, aminoglycosides, amphotericin B, cidofovir, foscarnet, indinavir, pentamidine, ritonavir.

    		 Hepatotoxicity (liver damage)
    delavirdine, efavirenz, fluconazole, isoniazid, itraconazole, ketoconazole, nevirapine, NRTIs, protease inhibitors, rifabutin, rifampin.

    Rash
    abacavir, cotrimoxazole, dapsone, NNRTIs, protease inhibitors.

    Diarrhea
    didanosine, clindamycin, nelfinavir, ritonavir.

    Ocular (eye) Effects
    didanosine, ethambutol, rifabutin, cidofovir.

    Based on Department of Health and Human Services
      April 2000 May
      Copyright © 2000 HIV Plus
      All rights reserved.
      Last modified 3/28/2000.    		 HIV PLUS