Fosamprenavir and Rifampin interaction
Fosamprenavir and Rifampin: both prescribing labels flag this combination with the strongest language, such as a contraindication, a boxed warning, or an instruction to avoid it.
Do not combine without a prescriber's guidance. The label language below is the strongest FDA uses.
What the FDA labels say
From the Fosamprenavir (Fosamprenavir Calcium) label · effective 2026-06-30
…coadministered with the following drugs: Alpha 1-adrenoreceptor antagonist: Alfuzosin Antiarrhythmics: Flecainide (with ritonavir ), propafenone (with ritonavir ) Antimycobacterial: Rifampin Antipsychotic: Lurasidone (with ritonavir ), pimozide Ergot derivatives: Dihydroergotamine, ergonovine, ergotamine, methylergonovine GI motility agent: Cisapride Herbal product:…
Antimycobacterial: Rifampin a ↓Amprenavir Coadministration is contraindicated as it may lead to loss of virologic response and possible resistance to Fosamprenavir calcium or to the class of protease inhibitors [see Contraindications (4)].
Initiation of medications that inhibit or induce CYP3A may increase or decrease concentrations of fosamprenavir calcium/ritonavir, respectively.
Coadministration of fosamprenavir calcium with drugs that induce CYP3A4 may decrease amprenavir (active metabolite) concentrations leading to potential loss of virologic activity.
Coadministration of fosamprenavir calcium and drugs that induce CYP3A4, such as rifampin, may decrease amprenavir concentrations and reduce its therapeutic effect.
From the Rifampin label · effective 2026-05-05
(See PRECAUTIONS, Drug Interactions .) Rifampin is contraindicated in patients who are also receiving atazanavir, darunavir, fosamprenavir, saquinavir, tipranavir, cabotegravir, fostemsavir and lenacapavir (see prescribing information for SUNLENCA ® ) due to the potential of rifampin to substantially decrease plasma concentrations of these antiviral drugs, which…
…Concentrations Administered with rifampin 600 mg daily, unless otherwise specified AUC = area under the time-concentration curve Drug or Drug Class and Prevention or Management Clinical Effect Antiretrovirals Prevention or Management: Concomitant use is contraindicated (see CONTRAINDICATIONS ) Atazanavir Decrease AUC by 72% Darunavir Rifampin dosage used concomitantly with…
Cabotegravir Decrease AUC by 59% Fostemsavir Decrease AUC by 82% Lenacapavir (SUNLENCA) Indicated for the treatment of human immunodeficiency virus-1 (HIV-1) infection Decrease AUC by 84% Antiretrovirals Prevention or Management: Avoid concomitant use Zidovudine Decrease AUC by 47% Indinavir Decrease AUC by 92% Efavirenz Decrease AUC by 26% Antiretrovirals Prevention…
Tipranavir Fosamprenavir Administered with rifampin 300 mg daily Decrease AUC by 82% Saquinavir Decrease AUC by 70% Coadministration may result in severe hepatocellular toxicity.
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Open in the checkerNot medical advice. Interaction Checker quotes FDA label text and NIH fact sheets. Whether an interaction matters for you depends on doses, timing, kidney and liver function, and other conditions. Confirm with a pharmacist or prescriber.