Efavirenz, lamivudine, and tenofovir and Levonorgestrel and ethinyl estradiol interaction
Efavirenz, lamivudine, and tenofovir and Levonorgestrel and ethinyl estradiol: both prescribing labels describe an interaction that usually calls for monitoring, a dose change, or spacing the doses.
Usually manageable with monitoring or a dose change. Tell your pharmacist you take both.
What the FDA labels say
From the Levonorgestrel and ethinyl estradiol (Tyblume) label · effective 2026-08-27
Enzyme inducers (e.g., CYP3A4) : May decrease the effectiveness of TYBLUME or increase breakthrough bleeding.
Metabolic Enzyme Inducers Clinical effect Concomitant use of CHCs with metabolic enzyme inducers may decrease the plasma concentrations of the estrogen and/or progestin component of CHCs [see Clinical Pharmacology (12.3) ] .
CYP3A inhibitors such as itraconazole, voriconazole, fluconazole, grapefruit juice The effect of grapefruit juice on CYP3A4 enzymes (e.g., strong vs. moderate inhibition) depends on its brand, concentration, and preparation. , or ketoconazole may increase systemic exposure of the estrogen and/or progestin component of CHCs.
Examples Aprepitant, barbiturates, bosentan, carbamazepine, efavirenz, felbamate, griseofulvin, oxcarbazepine, phenytoin, rifampin, primidone, phenylbutazone, rifabutin, rufinamide, topiramate, products containing St.
Counsel patients to use a back-up or alternative method of contraception when enzyme inducers are used with TYBLUME.
From the Efavirenz, lamivudine, and tenofovir (SYMFI) label · effective 2019-10-15
Hormonal contraceptives: Oral Ethinyl estradiol/ Norgestimate ↓ active metabolites of norgestimate A reliable method of barrier contraception should be used in addition to hormonal contraceptives.
Implant Etonogestrel ↓ etonogestrel A reliable method of barrier contraception should be used in addition to hormonal contraceptives.
There have been postmarketing reports of contraceptive failure with etonogestrel in EFV-exposed patients.
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.