Efavirenz and Rifampin interaction
Efavirenz and Rifampin: 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 Efavirenz label · effective 2024-03-31
Not recommended with ATRIPLA, which contains efavirenz, emtricitabine, and tenofovir disoproxil fumarate, unless needed for dose adjustment when coadministered with rifampin.
Coadministration with Related Products Coadministration of efavirenz with ATRIPLA (efavirenz 600 mg/emtricitabine 200 mg/tenofovir disoproxil fumarate 300 mg) is not recommended unless needed for dose adjustment (e.g., with rifampin), since efavirenz is one of its active ingredients.
Potential for Other Drugs to Affect Efavirenz Drugs that induce CYP3A activity (e.g., phenobarbital, rifampin, rifabutin) would be expected to increase the clearance of efavirenz resulting in lowered plasma concentrations [ see Dosage and Administration ( 2.2 ) ].
Antimycobacterial: Rifabutin Rifampin ↓ rifabutin * ↓ efavirenz * Increase daily dose of rifabutin by 50%.
Increase efavirenz to 800 mg once daily when coadministered with rifampin to patients weighing 50 kg or more.
From the Rifampin label · effective 2026-05-05
…Concentrations Administered with rifampin 600 mg daily, unless otherwise specified AUC = area under the time-concentration curve Drug or Drug Class and Prevention or Management Clinical Effect Antiretrovirals Prevention or Management: Concomitant use is contraindicated (see CONTRAINDICATIONS ) Atazanavir Decrease AUC by 72% Darunavir Rifampin dosage used concomitantly with…
Cabotegravir Decrease AUC by 59% Fostemsavir Decrease AUC by 82% Lenacapavir (SUNLENCA) Indicated for the treatment of human immunodeficiency virus-1 (HIV-1) infection Decrease AUC by 84% Antiretrovirals Prevention or Management: Avoid concomitant use Zidovudine Decrease AUC by 47% Indinavir Decrease AUC by 92% Efavirenz Decrease AUC by 26% Antiretrovirals Prevention…
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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.