Posaconazole and Rifabutin interaction
Posaconazole and Rifabutin: 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 Posaconazole (NOXAFIL) label · effective 2026-02-13
Rifabutin Avoid concomitant use of posaconazole with rifabutin unless the benefit to the patient outweighs the risk.
Prevention or Management Avoid concomitant use of posaconazole with rifabutin unless the benefit outweighs the risk.
See Table 17 for rifabutin monitoring considerations when posaconazole affects rifabutin via CYP3A4 inhibition.
Concomitant use of posaconazole with rifabutin increased rifabutin plasma concentrations [see Clinical Pharmacology (12.3) ].
Frequent monitoring of full blood counts and adverse reactions due to increased rifabutin plasma concentrations (e.g., uveitis, leukopenia) during concomitant use are recommended.
From the Rifabutin label · effective 2026-09-01
Posaconazole 200 mg once a day for 10 days 300 mg once a day for 17 days Healthy subjects (8) ↑ AUC by 72%, ↑ C max by 31% ↓ AUC by 49%, ↓ C max by 43% If co-administration of these two drugs cannot be avoided, patients should be monitored for adverse events associated with rifabutin administration, and lack of posaconazole efficacy.
Effect of Other Drugs on Rifabutin Pharmacokinetics Some drugs that inhibit CYP3A may significantly increase the plasma concentration of rifabutin.
Therefore, carefully monitor for rifabutin associated adverse events in those patients also receiving CYP3A inhibitors, which include fluconazole and clarithromycin.
In some cases, the dosage of rifabutin may need to be reduced when it is co-administered with CYP3A inhibitors.
ANTIFUNGALS Fluconazole 200 mg once a day for 2 weeks 300 mg once a day for 2 weeks HIV-infected patients (12) ↑ AUC by 82%, ↑ C max by 88% ↔ Monitor for rifabutin associated adverse events.
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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.