Etravirine and Fosamprenavir interaction
Etravirine and Fosamprenavir: 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 Etravirine label · effective 2025-04-02
…unknown Co-administration of Etravirine with darunavir/cobicistat is not recommended because it may result in loss of therapeutic effect and development of resistance to darunavir. fosamprenavir (without ritonavir) ↑ amprenavir Concomitant use of Etravirine with fosamprenavir without low-dose ritonavir may cause a significant alteration in the plasma concentration…
Co-administration of Etravirine and fosamprenavir without low-dose ritonavir is not recommended. fosamprenavir/ritonavir ↑ amprenavir Due to a significant increase in the systemic exposure of amprenavir, the appropriate doses of the combination of Etravirine and fosamprenavir/ritonavir have not been established.
Co-administration of Etravirine and fosamprenavir/ritonavir is not recommended. indinavir (without ritonavir) ↓ indinavir Concomitant use of Etravirine with indinavir without low-dose ritonavir may cause a significant alteration in the plasma concentration of indinavir.
HIV-antiviral agents: protease inhibitors (PIs) atazanavir (without ritonavir) ↓ atazanavir Co-administration of Etravirine and atazanavir without low-dose ritonavir is not recommended. atazanavir/ritonavir ↓ atazanavir ↔ etravirine Concomitant use of Etravirine with atazanavir/ritonavir decreased atazanavir C min but it is not considered clinically relevant.
CCR5 antagonists maraviroc ↔ etravirine ↓ maraviroc When Etravirine is co-administered with maraviroc in the absence of a potent CYP3A inhibitor (e.g., ritonavir boosted protease inhibitor), the recommended dose of maraviroc is 600 mg twice daily.
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.
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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.