Bosentan and Fosamprenavir interaction
Bosentan 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 Bosentan (Tracleer) label · effective 2025-11-17
Co-administration of such combinations of a CYP2C9 inhibitor plus a strong or moderate CYP3A inhibitor with TRACLEER is not recommended.
Concomitant administration of both a CYP2C9 inhibitor (such as fluconazole or amiodarone) and a strong CYP3A inhibitor (e.g., ketoconazole, itraconazole) or a moderate CYP3A inhibitor (e.g., amprenavir, erythromycin, fluconazole, diltiazem) with TRACLEER will likely lead to large increases in plasma concentrations of bosentan.
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.
Endothelin-receptor antagonist: Bosentan ↑ Bosentan Coadministration of bosentan in patients on fosamprenavir calcium: In patients who have been receiving fosamprenavir calcium for at least 10 days, start bosentan at 62.5 mg once daily or every other day based upon individual tolerability.
Coadministration of fosamprenavir calcium in patients on bosentan: Discontinue use of bosentan at least 36 hours prior to initiation of fosamprenavir calcium.After at least 10 days following the initiation of fosamprenavir calcium, resume bosentan at 62.5 mg once daily or every other day based upon individual tolerability.
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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.