Efavirenz, lamivudine, and tenofovir and Nifedipine interaction
Efavirenz, lamivudine, and tenofovir and Nifedipine: 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 Nifedipine label · effective 2026-02-05
John’s Wort reduce the bioavailability and efficacy of nifedipine; therefore nifedipine should not be used in combination with strong CYP3A inducers such as rifampin (See CONTRAINDICATIONS ).
…as ketoconazole, fluconazole, itraconazole, clarithromycin, erythromycin (Azithromycin, although structurally related to the class of macrolide antibiotic is void of clinically relevant CYP3A4 inhibition), grapefruit, nefazodone, fluoxetine, saquinavir, indinavir, nelfinavir, and ritonavir may result in increased exposure to nifedipine when co-administered.
Verapamil: Verapamil, a CYP3A inhibitor, can inhibit the metabolism of nifedipine and increase the exposure to nifedipine during concomitant therapy.
Non-Cardiovascular Drugs Antifungal Drugs Ketoconazole, itraconazole and fluconazole are CYP3A inhibitors and can inhibit the metabolism of nifedipine and increase the exposure to nifedipine during concomitant therapy.
Erythromycin: Erythromycin, a CYP3A inhibitor, can inhibit the metabolism of nifedipine and increase the exposure to nifedipine during concomitant therapy.
From the Efavirenz, lamivudine, and tenofovir (SYMFI) label · effective 2019-10-15
Calcium channel blockers: Diltiazem ↓ diltiazem ↓ desacetyl diltiazem ↓ N-monodesmethyldiltiazem Diltiazem dose adjustments should be guided by clinical response (refer to the full prescribing information for diltiazem).
Others (e.g., felodipine, nicardipine, nifedipine, verapamil) ↓ calcium channel blocker When coadministered with EFV, dosage adjustment of calcium channel blocker may be needed and should be guided by clinical response (refer to the full prescribing information for the calcium channel blocker).
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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.