Efavirenz, lamivudine, and tenofovir and Norethindrone and ethinyl estradiol interaction
Efavirenz, lamivudine, and tenofovir and Norethindrone and ethinyl estradiol: 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 Norethindrone and ethinyl estradiol (Lo Loestrin Fe) label · effective 2025-03-07
Counsel patients to use a back-up method or alternative method of contraception when enzyme inducers are used with COCs ( 7.1 ) -- - ---------- ------ USE IN SPECIFIC POPULATIONS---- -- -- --------- ---- Lactation: Not recommended; Lo Loestrin Fe can decrease milk production ( 8.2 )
CYP3A4 inhibitors such as itraconazole or ketoconazole may increase plasma hormone levels.
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.