EFV

EFV most commonly refers to efavirenz, a non-nucleoside reverse transcriptase inhibitor (NNRTI) used in antiretroviral therapy for HIV-1 infection. It is marketed under brand names such as Sustiva and is widely included in first-line regimens in combination with other antiretrovirals, often with two nucleoside reverse transcriptase inhibitors.

Efavirenz works by binding directly to the HIV-1 reverse transcriptase enzyme, inhibiting viral RNA-dependent DNA synthesis and thereby reducing viral replication. It is typically taken orally once daily, with or without food, though food can increase absorption and affect tolerability. The drug has a long plasma half-life of about 40 to 55 hours, which supports once-daily dosing but may contribute to prolonged central nervous system side effects in some patients.

Common adverse effects include dizziness, sleep disturbances, vivid dreams, and rash. Hepatotoxicity and rare but serious psychiatric symptoms can occur. Efavirenz is teratogenic in animal studies and is generally approached with caution in pregnancy; avoidance during the first trimester is common, and effective contraception is advised for those of childbearing potential. Drug interactions are frequent due to metabolism by hepatic enzymes, particularly CYP2B6 and CYP3A4. Inducers such as rifampin or certain anticonvulsants can reduce efavirenz levels, while other agents may increase exposure.

In addition to efavirenz, the acronym EFV may appear in other contexts, but efavirenz is the primary medical meaning in HIV treatment. Usage and guidelines vary by country and over time.