Rifabutin and Ritonavir interaction
Rifabutin and Ritonavir: 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 Rifabutin label · effective 2026-09-01
Therefore, co-administration with antiretroviral and anti-HCV drugs metabolized by CYP3A is not recommended or there may be a need to increase the dose of antiretroviral or anti-HCV drugs (see PRECAUTIONS-Drug Interactions ).
Fosamprenavir/ritonavir 700 mg twice a day plus ritonavir 100 mg twice a day for 2 weeks 150 mg every other day for 2 weeks Healthy subjects (15) ↔ AUC compared to rifabutin 300 mg once a day alone ↓ C max by 15% ↑ AUC by 35% compared to historical control (fosamprenavir/ritonavir 700/100 mg twice a day) , ↑ C max by 36%, ↑ C min by 36% Reduce rifabutin dose…
Lopinavir/ ritonavir 400/100 mg twice a day for 20 days 150 mg once a day for 10 days Healthy subjects (14) ↑ AUC by 203% also taking zidovudine 500 mg once a day ↓ C max by 112% ↔ Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with lopinavir/ritonavir combination.
Saquinavir/ritonavir 1000/100 mg twice a day for 14 or 22 days 150 mg every 3 days for 14 or 22 days Healthy subjects ↑ AUC by 53% compared to rifabutin 150 mg once a day alone ↑ C max by 88% (n=11) ↓ AUC by 13%, ↓ C max by 15%, (n=19) Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with saquinavir/ritonavir…
Ritonavir 500 mg twice a day for 10 days 150 mg once a day for 16 days Healthy subjects (5) ↑ AUC by 300%, ↑ C max by 150% ND Reduce rifabutin dose by at least 75% (to a maximum 150 mg every other day or three times per week) when given with lopinavir/ritonavir combination.
From the Ritonavir (Norvir) label · effective 2026-07-23
Antimycobacterial: rifabutin ↑ rifabutin and rifabutin metabolite Dosage reduction of rifabutin by at least three-quarters of the usual dose of 300 mg per day is recommended (e.g., 150 mg every other day or three times a week).
Alternate antimycobacterial agents such as rifabutin should be considered.
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.