levonorgestrel + efavirenz

Levonorgestrel + efavirenz refers to the co-administration of two pharmaceutical agents with distinct indications and mechanisms. Levonorgestrel is a synthetic progestogen used primarily for emergency contraception and as a component in contraceptive implants. It acts by inhibiting ovulation and altering cervical mucus to prevent fertilization. Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI) used in combination antiretroviral therapy for HIV-1 infection; it inhibits viral replication by binding to and inhibiting the HIV-1 reverse transcriptase enzyme[3]. When administered together, efavirenz induces hepatic enzymes (notably CYP3A4), which accelerates the metabolism of levonorgestrel, leading to significantly reduced plasma concentrations of levonorgestrel[2][5][6][8]. This interaction can compromise contraceptive efficacy. Clinical studies have shown that doubling the dose of levonorgestrel may partially compensate for this reduction but may not fully restore effectiveness in all individuals[4][5][8].

Brand names

AtriplaStocrinSymfi