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Anti-HIV Drug Interactions
A Guide to the Interactions Found Between Anti-HIV Drugs and Common HIV-Related Therapies

August 2004

Interactions Table (A)

B-D | E-I | K-P | R | S-Z


Abacavir (Ziagen) plus ...
3TC Decreases 3TC level by 15% in blood. No dose adjustment recommended.
Alcohol Should be used together with caution. Increases abacavir level by 41% in blood. No dose adjustment recommended.
Amprenavir Increases amprenavir level by 29% in blood. No dose adjustment recommended.
AZT Increases AZT level by 10% in blood. No dose adjustment recommended.
Chloral hydrate Should be used together with caution. May increase chloral hydrate level in blood.
Methadone May decrease methadone level in blood. Check for methadone withdrawal symptoms and adjust methadone dose accordingly.
Tenofovir Should be used together with caution. Although blood levels not affected, tenofovir and abacavir used in combination may speed the development of resistance to both.

Acyclovir (Zovirax) plus ...
Probenecid Increases acyclovir level in blood.

Adefovir (Hepsera) plus ...
Amikacin Should not be used together. Increases risk of kidney toxicity.
Amphotericin B Should not be used together*. Increases risk of kidney toxicity.
Cidofovir Should not be used together*. Increases risk of kidney toxicity.
Foscarnet Should not be used together*. Increases risk of kidney toxicity.
Gentamicin Should not be used together*. Increases risk of kidney toxicity.
Ibuprofen Should be used together with caution. Increases adefovir level by 23% in blood and may increase risk of kidney toxicity.
Kanamycin Should not be used together*. Increases risk of kidney toxicity.
NSAIDS Should not be used together*. May increase risk of kidney toxicity.
Pentamidine (IV) Should not be used together*. Increases risk of kidney toxicity.
Tenofovir Should not be used together*. Increases risk of kidney toxicity.
Tobramycin Should not be used together*. Increases risk of kidney toxicity.

Amphotericin B (Fungizone) plus ...
Adefovir Should not be used together.* Increases risk of kidney toxicity.
Amikacin Should be used together with great caution. May increase risk of kidney toxicity.
Anticancer drugs Should be used together with great caution. May increase risk of kidney toxicity and low blood pressure.
AZT May increase risk of bone marrow toxicity.
Cidofovir Should not be used together*. Increases risk of kidney toxicity.
Clotrimazole May interfere with the activity of amphotericin B.
Corticosteroids Should be used together with caution. May decrease potassium level and increases risk of heart problems.
Cyclosporine Should be used together with great caution. May increase risk of kidney toxicity.
ddC May increase ddC level in blood and increase risk of peripheral neuropathy.
Digitalis Use together with great caution. May increase risk of heart problems.
Fluconazole May interfere with the activity of amphotericin B.
Flucytosine Increases antifungal activity in test tubes but also increases risk of bone marrow and kidney toxicity.
Foscarnet Should be used together with great caution. May decrease number of red blood cells and increases risk of kidney toxicity.
Ganciclovir Should be used together with great caution. May increase risk of bone marrow toxicity.
Gentamicin Should be used together with great caution. May increase risk of kidney toxicity.
Itraconazole May interfere with the activity of amphotericin B.
Kanamycin Should be used together with great caution. May increase risk of kidney toxicity.
Ketoconazole May interfere with the activity of amphotericin B.
Miconazole May interfere with the activity of amphotericin B.
Pentamidine (IV) Should be used together with great caution. May increase risk of kidney toxicity.
Tenofovir Should not be used together*. May increase risk of side effects.
Tobramycin Should be used together with great caution. May increase risk of kidney toxicity.

Amprenavir (Agenerase) plus ...
Abacavir Increases amprenavir level by 29% in blood. No dose adjustment recommended.
Alcohol Should not be used together. Alcohol and the oral formulation of amprenavir increases risk of side effects.
Alprazolam May increase alprazolam level in blood.
Amiodarone Should be used together with caution. May increase risk of side effects. Requires monitoring concentration of amiodarone.
Antacids Amprenavir should be taken 1 hour before or 1 hour after taking antacids.
Astemizole Should not be used together*. Increases risk of side effects.
Atazanavir Atazanavir may increase amprenavir levels in blood.
Atorvastatin Should be used together with great caution. May increase atorvastatin level in blood.
AZT Increases AZT level by 31% and increases amprenavir level by 13% in blood. No dose adjustment recommended.
Bepridil Should not be used together*. Increases risk of side effects.
Carbamazepine Should be used together with caution. May decrease amprenavir level in blood.
Cimetidine May increase amprenavir level in blood.
Cisapride Should not be used together*. Increases risk of side effects.
Clarithromycin Increases amprenavir level by 18% in blood. No dose adjustment recommended.
Clorazepate May increase clorazepate level in blood.
Clozapine May increase clozapine level in blood.
Dapsone May increase dapsone level in blood.
ddI or ddI EC Should be taken 1 hour before or after taking ddI tablets. ddI EC may be taken at the same time as amprenavir, but only on an empty stomach.
Delavirdine May increase amprenavir level in blood. No dose adjustment recommended.
Diazepam May increase diazepam level in blood.
Dihydroergotamine Should not be used together*. Increases risk of side effects.
Diltiazem May increase diltiazem level in blood.
Disulfiram Should not be used together with amprenavir oral solution*. Increases risk of side effects.
Efavirenz Decreases amprenavir level by 36% and increases efavirenz level by 15% in blood. Amprenavir dose may need to be increased.
Ergotamine Should not be used together*. Increases risk of side effects.
Erythromycin May increase erythromycin and amprenavir levels in blood.
Ethinyl estradiol Should not be used together. Amprenavir may decrease ethinyl estradiol and norethindrone levels in blood. Use another form of contraception.
Felodipine May increase felodipine level in blood.
Flurazepam May increase flurazepam level in blood.
Food (high fat) Decreases amprenavir level in blood and should be avoided.
Indinavir Increases amprenavir level by 33% and decreases indinavir level by 38% in blood. No dose adjustment recommended.
Itraconazole May increase itraconazole and amprenavir level in blood. Check for toxicity.
Kaletra Decreases lopinavir level by 15% and increases amprenavir trough level about 2-fold in blood. Amprenavir dose should be reduced to 750 mg twice a day or less. However, optimal dose is unclear.
Ketoconazole Increases amprenavir level by 31% and increases ketoconazole level by 44% in blood. Impact of interaction is uncertain.
Lidocaine (systemic) Should be used together with caution. Requires monitoring concentration of lidocaine.
Loratidine May increase loratidine level in blood.
Lovastatin Should be used together with great caution. May increase lovastatin level in blood.
Metronidazole Should not be used together with amprenavir oral solution*. Increases risk of side effects.
Midazolam Should not be used together*. Increases risk of side effects.
Nelfinavir Increases nelfinavir level by 15% in blood. No dose adjustment recommended.
Nevirapine May decrease amprenavir level in blood. Dose of amprenavir may need to be increased.
Norethindrone Should not be used together. Amprenavir may decrease ethinyl estradiol and norethindrone levels in blood. Use another form of contraception.
Nicardipine May increase nicardipine level in blood.
Nifedipine May increase nifedipine level in blood.
Nimodipine May increase nimodipine level in blood.
Phenobarbital Should be used together with caution. May decrease amprenavir level in blood.
Phenytoin Should be used together with caution. May decrease amprenavir level in blood.
Pimozide May increase pimozide level in blood.
Pravastatin Should be used together with great caution. May increase pravastatin level in blood.
Quinidine Should be used together with caution. Requires monitoring concentration of quinidine.
Rifabutin Decreases amprenavir level by 15% and increases rifabutin level by 193% in blood. A lower dose of rifabutin required.
Rifampin Should not be used together*. Significantly decreases amprenavir level in blood.
Ritonavir Increases amprenavir level by 70% in blood. Alternate dosing is amprenavir 600 mg + ritonavir 100 mg twice a day, or amprenavir 1,200 mg + ritonavir 200 mg once daily.
Saquinavir (Fortovase) Decreases amprenavir level by 32% and saquinavir level by 19% in blood. No dose adjustment likely required.
Sildenafil Should be used together with caution. May increase sildenafil level in blood.
Simvastatin Should be used together with great caution. May increase simvastatin level in blood.
St. John's Wort Should be used together with great caution. May significantly decrease amprenavir level in blood.
Tedalafil Should be used together with caution. May increase tedalafil level in blood.
Triazolam Should not be used together*. Increases risk of side effects.
Tricyclic antidepressants Should be used together with caution. Requires monitoring concentration of tricyclic antidepressants.
Vardenafil Should be used together with caution. May increase vardenafil level in blood.
Vitamin E Amprenavir capsules contain more than the recommended daily allowance for vitamin E. Additional supplementation, especially when used together with drugs like warfarin could result in hemorrhage.
Warfarin Should be used together with caution. Requires monitoring concentration of warfarin.

Atazanavir (Reyataz) plus...
Amiodarone Increases risk of side effects. Check amiodarone level and use with caution.
Amprenavir Atazanavir may increase amprenavir levels in blood.
Antacids May decrease atazanavir level in blood. Take atazanavir 2 hours before or 1 hour after taking antacids.
Atorvastatin Should be used together with great caution. May increase risk of side effects.
Bepridil Should not be used together*. Increases risk of side effects.
Calcium channel blockers Should be used together with great caution. Decrease dose of calcium channel blockers and check ECG.
Cisapride Should not be used together*. Increases risk of side effects.
Clarithromycin Increases risk of side effects and may decrease effectiveness of clarithromycin. Consider alternatives or reduce clarithromycin dose by at least 50%.
Cyclosporin Should be used together with caution. Check cyclosporine level.
ddI or ddI EC ddI buffered tablets can significantly decrease atazanavir level in blood. Take atazanavir (with food) either 2 hours before or 1 hour after buffered ddI tablets. Although ddI EC should not affect atazanavir level, they should be taken at least 1 hour apart. Atazanavir should be taken with food, and ddI EC should be taken on an empty stomach.
Diltiazem Should be used together with great caution. Decrease diltiazem dose by at least 50% and check ECG.
Ergot derivatives Should not be used together*. Increases risk of side effects.
Efavirenz Decreases atazanavir level in blood. Atazanavir should be boosted with ritonavir if used with efavirenz.
Ethinyl estradiol Should be used together with caution. Atazanavir increases ethinyl estradiol level in blood. Use lowest effective ethinyl estradiol dose.
Food High fat meal increases atazanavir by 35% and low fat meal increases atazanavir level by 70% in blood. Atazanavir should be taken with food.
Indinavir Should not be used together*. Increases risk of side effects.
Irinotecan Atazanavir may interfere with irinotecan metabolism. May increase irinotecan side effects.
Lidocaine (systemic) Increases risk of side effects. Check lidocaine level and use with caution.
Lovastatin Should not be used together*. Increases risk of side effects.
Midazolam Should not be used together*. Increases risk of side effects.
Norethindrone Should be used together with caution and decrease norethindrone dose to lowest effective dose. May increase norethindrone side effects, particularly in diabetic women.
Pimozide Should not be used together*. Increases risk of side effects.
Proton-pump inhibitors Should not be used together. May significantly decrease atazanavir level in blood.
Quinidine Increases risk of side effects. Check quinidine level and use with caution.
Rifabutin Increases rifabutin level. Decrease dose of rifabutin to 150 mg every other day or 3 times a week.
Rifampin Should not be used together. Decreases level of most protease inhibitors in blood.
Ritonavir Substantially increases atazanavir blood level. If combined, use atazanavir 300 mg (with food) + ritonavir 100 mg once daily.
Saquinavir (Fortovase) Increases saquinavir level by 5–6 fold in blood. Dose adjustments currently under study.
Sildenafil Increases sildenafil blood level. Decrease sildenafil dose to 25 mg every 48 hrs and check for side effects.
Simvastatin Should not be used together*. Increases risk of side effects.
Sirolimus Should be used together with caution. Check sirolimus level.
St. John's Wort Should not be used together. May reduce atazanavir level in blood.
Tacrolimus Should be used together with caution. Check tacrolimus level.
Tedalafil Should be used together with caution. May increase tedalafil level in blood.
Tenofovir Increases tenofovir level by 24% and decreases atazanavir level by up to 40% in blood. Atazanavir should be boosted with ritonavir if used with tenofovir.
Triazolam Should not be used together*. Increases risk of side effects.
Tricyclic antidepressants Increases risk of side effects. Check anti-depressant level and use with caution.
Vardenafil Should be used together with caution. May increase vardenafil level in blood.
Warfarin Should be used together with great caution. Has not been studied but may lead to serious side effects.

Atovaquone (Mepron) plus ...
AZT Increases AZT level by 35% in blood. No dose adjustment recommended.
Fatty foods Increases atovaquone level in blood. Atovaquone should be taken with food.
Kaletra Decreases atovaquone level in blood. Atovaquone dose may have to be increased.
Rifabutin Should be used together with caution. May decrease atovaquone level in blood.
Rifampin Should be used together with caution. Decreases atovaquone level by 50% in blood.
Ritonavir May decrease atovaquone level in blood.
TMP/SMX Increases TMP/SMX blood level by 17% and 8%, respectively. No dose adjustment recommended.

Azithromycin (Zithromax) plus ...
AZT May increase AZT level in blood. No dose adjustment recommended.
Cyclosporine May increase cyclosporine level in blood.
ddI or ddI EC May increase ddI level in blood. No dose adjustment recommended.
Digoxin May increase digoxin level in blood.
Ergot derivatives May increase ergot drug level in blood.
Food Azithromycin may be taken with or without food.
Hexobarbital May increase hexobarbital level in blood.
Midazolam May increase midazolam level in blood. No dose adjustment recommended.
Nelfinavir Should be used together with caution. Increases azithromycin level in blood. No dose adjustment recommended, but check for hearing and liver side effects.
Phenytoin May increase phenytoin level in blood.
Rifabutin May increase rifabutin level in blood. No dose adjustment recommended.
Theophylline May increase theophylline level in blood. No dose adjustment recommended.
Terfenadine May increase terfenadine level in blood.
Warfarin May increase warfarin level in blood.


Interpreting Directions

Should not be used together
The risk of side effects from a combination is too high for the two medications to be used together.

An asterisk (*) following this phrase means the side effects may be life-threatening.

Should be used together with caution
The risk of side effects from a combination is possible, but not highly common.

Should be used together with great caution
The risk of side effects from a combination is possible, and though not common may be serious if they occur.


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