Anti-HIV Drug Interactions

Interactions Table (S-Z)

Saquinavir (Fortovase, soft gel capsule) plus ...
Amprenavir	Decreases amprenavir level by 32% and saquinavir level by 19% in blood. No dose adjustment likely required.
Astemizole	Should not be used together*. Increases risk of side effects.
Atazanavir	Increases saquinavir level by 5–6 fold in blood. Dose changes now under study.
Atorvastatin	Should be used together with great caution. Ritonavir + saquinavir increases atorvastatin level by 343% in blood.
Carbamazepine	Should be used together with great caution. May decrease saquinavir level in blood.
Cisapride	Should not be used together*. Increases risk of side effects.
Clarithromycin	Increases saquinavir level by 177% and increases clarithromycin level by 45% (but decreases 14-hydroxy clarithromycin level by 24%) in blood. No dose adjustments currently recommended.
Dihydroergotamine	Should not be used together*. Increases risk of side effects.
Delavirdine	Increases saquinavir level by 5 times in blood. Reduce saquinavir dose to 800 mg 3 times/day.
Dexamethasone	Should be used together with caution. May decrease saquinavir level in blood.
ddI or ddI EC	Saquinavir should be taken 2 hours before or after taking ddI or ddI EC. Saquinavir is best taken with food, and ddI and ddI EC should only be taken on an empty stomach.
Efavirenz	Decreases efavirenz level by 12% and saquinavir level by 62% in blood. Requires ritonavir boosting.
Ergonovine	Should not be used together*. Increases risk of side effects.
Ergotamine	Should not be used together*. Increases risk of side effects.
Fluconazole	May increase saquinavir level in blood. However, no dose adjustment recommended.
Food	High fat meal increases saquinavir level by 93% in blood. Should be taken within 2 hours of a meal.
Garlic supplements	Should be used together with great caution. Decreases saquinavir level by 51% in blood.
Grapefruit juice	Increases saquinavir level in blood.
Indinavir	Increases saquinavir level 3.6–6.2 times in blood.
Itraconazole	Increases saquinavir level in blood. However, no dose adjustment recommended.
Kaletra	Increases saquinavir trough level by about 3-fold. Saquinavir dose may be reduced to 800 mg twice a day. Optimal dosing is under study.
Ketoconazole	Significantly increases saquinavir level in blood. However, no dose adjustment recommended.
Lovastatin	Should not be used together*. Increases risk of side effects.
Methylergonovine	Should not be used together*. Increases risk of side effects.
Miconazole	May increase saquinavir level in blood. However, no dose adjustment recommended.
Midazolam	Should not be used together*. Increases risk of side effects.
Nelfinavir	Increases nelfinavir level 18% and increases saquinavir level 4 times in blood. Saquinavir dose may be reduced to 800 mg 3 times a day or 1,200 mg twice a day.
Nevirapine	Decreases saquinavir level by 24% in blood. Saquinavir may require ritonavir boosting.
Phenobarbital	Should be used together with great caution. May decrease saquinavir level in blood.
Phenytoin	Should be used together with great caution. May decrease saquinavir level in blood.
Pravastatin	Ritonavir + saquinavir decreases pravastatin level by 47% in blood.
Rifabutin	Should be used together with great caution. Decreases saquinavir level by 40% in blood. Consider alternative to rifabutin.
Rifampin	Should not be used together. Decreases saquinavir level by 84% in blood.
Ritonavir	Increases saquinavir level by 1,587% in blood. Adjust doses to saquinavir 1,000 mg + ritonavir 100 mg twice a day.
Sildenafil	Should be used together with caution. Increases sildenafil level by 210% in blood. Start sildenafil at no more than 25 mg.
Simvastatin	Should not be used together*. May significantly increase simvastatin level in blood and increase risk of side effects. Ritonavir + saquinavir (soft gel) increases simvastatin level by 3,059% in blood.
St. John's Wort	Should not be used together. May decrease saquinavir 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.
Vardenafil	Should be used together with caution. May increase vardenafil level in blood.

Saquinavir (Invirase, hard gel capsule) plus ...
Astemizole	Should not be used together*. Increases risk of side effects.
Atorvastatin	Should be used together with great caution. Ritonavir + saquinavir (soft gel) increases atorvastatin level by 343%.
Bepridil	Should be used together with caution. May increase bepridil level in blood. Check for side effects.
Carbamazepine	Should not be used together. May decrease saquinavir level in blood.
Clindamycin	Should be used with caution. May increase clindamycin level in blood. Check for side effects.
Dapsone	May increase dapsone level in blood. Check for dapsone side effects.
ddI or ddI EC	Saquinavir should be taken 2 hours before or after taking ddI or ddI EC. Saquinavir is best taken with food, and ddI and ddI EC should only be taken on an empty stomach.
Delavirdine	Increases saquinavir level by 5 times in blood. May increase risk of GI side effects and LFTs. Reduce saquinavir dose to 800 mg 3 times a day.
Dexamethasone	Should be used together with caution. May decrease saquinavir level in blood.
Diltiazem	Should be used together with caution. May increase diltiazem level in blood. Check for side effects.
Felodipine	Should be used together with caution. May increase felodipine level in blood. Check for side effects.
Fluconazole	May increase saquinavir level in blood. However, no dose adjustment recommended.
Food	Increases saquinavir level in blood. Should be taken within 2 hours of a meal.
Grapefruit juice	Increases saquinavir level in blood.
Indinavir	Increases saquinavir level 4.6–7.2 times in blood.
Itraconazole	Increases saquinavir level in blood. However, no dose adjustment recommended.
Ketoconazole	Significantly increases saquinavir level in blood. However, no dose adjustment recommended.
Lovastatin	Should not be used together*. Increases risk of side effects.
Miconazole	May increase saquinavir level in blood. However, no dose adjustment recommended.
Nelfinavir	Increases saquinavir level by 4 times and increases nelfinavir level by 18% in blood. Saquinavir dose may be reduced to 800 mg 3 times a day or 1,200 mg twice a day.
Nevirapine	Decreases saquinavir level 24% in blood. Saquinavir may require ritonavir boosting.
Nicardipine	Should be used together with caution. May increase nicardipine level in blood. Check for side effects.
Nifedipine	Should be used together with caution. May increase nifedipine level in blood. Check for side effects.
Nimodipine	Should be used together with caution. May increase nimodipine level in blood. Check for side effects.
Nisoldipine	Should be used together with caution. May increase nisoldipine level in blood. Check for side effects.
Nitrendipine	Should be used together with caution. May increase nitrendipine level in blood. Check for side effects.
Phenobarbital	Should not be used together. May decrease saquinavir level in blood.
Phenytoin	Should not be used together. May decrease saquinavir level in blood.
Pravastatin	Ritonavir + saquinavir (soft gel) decreases pravastatin level by 47% in blood.
Quinidine	Should be used with caution. May increase quinidine level in blood. Check for side effects.
Rifabutin	Should be used together with great caution. Decreases saquinavir level by 40% in blood. Consider alternative to rifabutin.
Rifampin	Should not be used together. Decreases saquinavir level by 84% in blood.
Ritonavir	Increases saquinavir level by about 20 times in blood. Adjust doses to saquinavir 1,000 mg + ritonavir 100 mg twice a day.
Simvastatin	Should not be used together*. May significantly increase simvastatin level in blood and increase risk of side effects. Ritonavir + saquinavir (soft gel) increases simvastatin level by 3,059% in blood.
St. John's Wort	Should not be used together. May decrease saquinavir level in blood.
Triazolam	Should be used with caution. May increase triazolam level in blood. Check for side effects.

Sulfadiazine plus ...
Glipizide	Should be used together with caution. May decrease glipizide level in blood. Check blood sugar level and adjust dose accordingly.
Glyburide	Should be used together with caution. May decrease glyburide level in blood. Check blood sugar level and adjust dose accordingly.
Tolbutamide	Should be used together with caution. May decrease glyburide level in blood. Check blood sugar level and adjust dose accordingly.

Tenofovir (Viread) plus...
Abacavir	Should be used together with great caution. Although blood level not affected, tenofovir + abacavir speeds the development of resistance to both.
Adefovir	Should not be used together*. Increases risk of kidney toxicity.
Acyclovir	Should be used together with caution. May increase risk of kidney toxicity.
Amikacin	Should not be used together*. May increase risk of side effects.
Amphotericin B	Should not be used together*. May increase risk of side effects.
Atazanavir	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.
Cidofovir	Should not be used together*. May increase risk of side effects.
ddI or ddI EC	Should be used together with great caution. Increases ddI level by 44% in blood. May increase risk of ddI side effects.
Food (high fat meal)	Increases tenofovir level by 40% in blood. Tenofovir should be taken with food.
Foscarnet	Should be used together with great caution. May increase risk of kidney toxicity.
Ganciclovir	Should be used together with great caution. May increase risk of side effects. Check for kidney toxicity.
Gentamycin	Should not be used together*. May increase risk of side effects.
Kaletra	Increases tenofovir level by about 30% and decreases lopinavir level 15% in blood. No dose adjustment currently recommended.
Pentamidine (IV)	Should not be used together*. May increase risk of side effects.
Tobramycin	Should not be used together*. May increase risk of side effects.
Valacyclovir	Should be used together with caution. May increase risk of kidney toxicity.
Valganciclovir	Should not be used together*. May increase risk of side effects.

TMP/SMX (Bactrim, Septra) plus ...
3TC	Increases 3TC level by 44% in blood. No dose adjustment recommended. Check for 3TC side effects.
Anticancer drugs	May decrease number of red blood cells (anemia) and neutrophils (neutropenia).
AZT	Should be used together with caution. May decrease number of red blood cells (anemia) and neutrophils (neutropenia).
Dapsone	Increases trimethoprim level by 1.5 times and increases dapsone level by 1.5 times in blood.
ddI or ddI EC	Slightly decreases trimethoprim level and increases ddI level in blood. No dose adjustment recommended.
Diuretics	May decrease number of platelets in elderly people.
Ganciclovir	Should be used together with great caution. May increase risk of bone marrow toxicity.
Indinavir	Should be used together with caution. Increases trimethoprim level by 31% in blood.
Methotrexate	Should be used with caution. May increase methotrexate level in blood.
Nevirapine	Should not be started together for the first 4–6 weeks. May increase risk of rash.
Phenytoin	Should be used with caution. May increase phenytoin level in blood. Check for side effects.
Pyrimethamine	Should be used together with caution. May increase risk of bone marrow toxicity.
Warfarin	Should be used with caution. May increase prothrombin (coagulation) time. Check INR.

Trimetrexate (Neutrexin) plus ...
Acetaminophen	May affect trimetrexate and/or acetaminophen level in blood.
Cimetidine	May affect trimetrexate and/or cimetidine level in blood.
Clarithromycin	May affect trimetrexate and/or clarithromycin level in blood.
Erythromycin	May affect trimetrexate and/or erythromycin level in blood.
Fluconazole	May affect trimetrexate and/or fluconazole level in blood.
Itraconazole	May affect trimetrexate and/or itraconazole level in blood.
Ketoconazole	May affect trimetrexate and/or ketoconazole level in blood.
Ranitidine	May affect trimetrexate and/or ranitidine level in blood.
Rifabutin	Should be used together with caution. May affect trimetrexate and/or rifabutin level in blood.
Rifampin	Should be used together with caution. May affect trimetrexate and/or rifampin level in blood.

Trizivir plus ...

Trizivir is a single pill containing 3 anti-HIV drugs, 3TC, abacavir and AZT. If you take Trizivir as part of your regimen, refer separately to drug interactions for 3TC, abacavir and AZT.

Zalcitabine (ddC, Hivid) plus ...
3TC	Should not be used together. Decreases anti-HIV activity of both drugs.
Aminoglycosides	May increase ddC level in blood and increase risk of peripheral neuropathy. Check for toxicity.
Amphotericin B	May increase ddC level in blood and increase risk of peripheral neuropathy. Check for toxicity.
Antacids	Decreases ddC level by 25% in blood. Take at least 2 hours apart.
Anticancer drugs	May increase risk of peripheral neuropathy.
Chloramphenicol	May increase risk of peripheral neuropathy.
Cimetidine	Significantly increases ddC level in blood. Check for toxicity; consider lower ddC dose.
Cisplatin	May increase risk of peripheral neuropathy.
d4T	May increase risk of peripheral neuropathy and pancreatitis.
Dapsone	May increase risk of peripheral neuropathy.
ddI or ddI EC	Should not be used together. Significantly increases risk of peripheral neuropathy.
Disulfiram	May increase risk of peripheral neuropathy.
Doxorubicin	May decrease anti-HIV activity of ddC.
Ethionamide	May increase risk of peripheral neuropathy.
Food	May decrease ddC level in blood.
Foscarnet	May increase risk of kidney toxicity and peripheral neuropathy. Check for toxicity.
Glutethimide	May increase risk of peripheral neuropathy.
Hydralazine	May increase risk of peripheral neuropathy.
Iodoquinol	May increase risk of peripheral neuropathy.
Isoniazid	May increase risk of peripheral neuropathy.
Metoclopramide	Decreases ddC level by 10% in blood.
Metronidazole	May increase risk of peripheral neuropathy.
Nitrofurantoin	May increase risk of peripheral neuropathy.
Pentamidine (IV)	Should be used with great caution. May increase risk of peripheral neuropathy and pancreatitis.
Phenytoin	May increase risk of peripheral neuropathy.
Probenecid	Significantly increases ddC level in blood. Check for toxicity; consider lower ddC dose.
Ribavirin	May increase risk of peripheral neuropathy.
Vincristine	May increase risk of peripheral neuropathy.

Zidovudine (AZT, Retrovir) plus ...
Abacavir	Increases AZT level by 10% in blood. No dose adjustment recommended.
Amphotericin B	May increase risk of bone marrow toxicity.
Amprenavir	Increases AZT level by 31% and increases amprenavir level by 13% in blood. No dose adjustment recommended.
Anticancer drugs	May increase risk of bone marrow toxicity.
Atovaquone	Increases AZT level by 35% in blood. No dose adjustment recommended.
Azithromycin	May increase AZT level in blood. No dose adjustment recommended.
Clarithromycin	Decreases AZT level by 25% in blood. Consider taking at least 2 hours apart.
d4T	Should not be used together. Decreases anti-HIV activity.
Dapsone	May increase risk of bone marrow toxicity.
Doxorubicin	Should not be used together. Decreases effectiveness and increases toxicity.
Fluconazole	Increases AZT level by 74% and may increase fluconazole level in blood. Check for toxicity.
Flucytosine	May increase risk of bone marrow toxicity.
Food	Fatty foods may decrease AZT level by 57% in blood.
Foscarnet	Should be used together with caution. May increase risk of anemia.
Ganciclovir	Increases AZT level in blood and may increase risk of neutropenia, anemia and bone marrow toxicity. Avoid combination or use lower AZT dose.
Indinavir	Increases anti-HIV activity in test tubes. Increases AZT level by 17–36% in blood. No dose adjustment recommended.
Interferon-alfa	Increases anti-HIV activity in test tubes and may increase risk of bone marrow toxicity. Lower AZT dose by 50–75%.
Methadone	Increases AZT level by 43% in blood. Check for AZT toxicity.
Nelfinavir	Decreases AZT level by 35% in blood. No dose adjustment recommended.
Pentamidine	May increase risk of anemia.
Phenytoin	May decrease phenytoin and AZT levels in blood. No dose adjustment recommended.
Probenecid	Increases AZT level by 106% in blood. Adjusting AZT dose may be necessary.
Pyrimethamine	Should be used together with caution. May increase risk of bone marrow toxicity.
Ribavirin	Should not be used together. Decreases anti-HIV activity in test tubes.
Rifabutin	May decrease AZT level in blood.
Rifampin	Decreases AZT level by 47% in blood. May require increase in AZT dose.
Ritonavir	Decreases AZT level by 25% in blood. No dose adjustment recommended.
TMP/SMX	Should be used together with caution. May decrease number of red blood cells and neutrophils thus increasing risk of anemia.
Valproic Acid	Increases AZT level by 80% in blood. Check for AZT toxicity.
Vinblastine	May increase risk of bone marrow toxicity.
Vincristine	May increase risk of anemia.

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.