Fosamprenavir and Rifapentine interaction
Fosamprenavir and Rifapentine: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Fosamprenavir (Fosamprenavir Calcium) label · effective 2026-06-30
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.
Data also suggest that amprenavir induces CYP3A4.
Ritonavir also appears to induce CYP3A, CYP1A2, CYP2C9, CYP2C19, and CYP2B6, as well as other enzymes, including glucuronosyl transferase.
From the Rifapentine (Priftin) label · effective 2026-02-06
Concomitant use of rifapentine with other drugs metabolized by these enzymes, such as protease inhibitors, certain reverse transcriptase inhibitors, and hormonal contraception may cause a significant decrease in plasma concentrations and loss of therapeutic effect [see Drug Interactions (7.1 , 7.2 , 7.3 , 7.4) and Clinical Pharmacology (12.3) ] .
Concomitant use of PRIFTIN with other drugs metabolized by these enzymes, such as protease inhibitors and certain reverse transcriptase inhibitors, may cause a significant decrease in plasma concentrations and loss of therapeutic effect of the protease inhibitor or reverse transcriptase inhibitor [see Warnings and Precautions (5.6) and Clinical Pharmacology (12.3)…
Fixed-Dose Combination of Efavirenz, Emtricitabine, and Tenofovir Once-weekly coadministration of 900 mg PRIFTIN with the antiretroviral fixed-dose combination of efavirenz 600 mg, emtricitabine 200 mg and tenofovir disoproxil fumarate 300 mg in HIV-infected patients did not result in any substantial change in steady state exposures of efavirenz, emtricitabine,…
Protease Inhibitors and Reverse Transcriptase Inhibitors.
Protease Inhibitors and Reverse Transcriptase Inhibitors Rifapentine is an inducer of CYP450 enzymes.
Taking more than these two? Interactions stack. Check your whole list at once; it stays in your browser.
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.