Efavirenzbased

Efavirenz-based regimens are antiretroviral therapy (ART) regimens that use efavirenz as the anchor drug, typically combined with two nucleoside reverse transcriptase inhibitors (NRTIs). The most common backbone pairs include emtricitabine/tenofovir disoproxil fumarate (FTC/TDF) in fixed-dose products such as efavirenz/emtricitabine/tenofovir disoproxil fumarate. Efavirenz-based regimens have been widely used since the mid-2000s and have provided convenient once-daily dosing.

Pharmacology and mechanism of action: Efavirenz is a non-nucleoside reverse transcriptase inhibitor (NNRTI). It binds to an allosteric site on reverse transcriptase, inhibiting viral replication. It is extensively metabolized by cytochrome P450 enzymes, particularly CYP3A4, which also means it has the potential for multiple drug interactions. Efavirenz has a relatively long half-life, contributing to once-daily dosing but also to prolonged exposure if adverse effects occur.

Clinical use and positioning: Efavirenz-based regimens achieved durable viral suppression and were widely recommended as first-line therapy in many guidelines for years. Today, they remain in use, especially where cost, availability, or specific patient considerations favor them. However, due to tolerability concerns and drug interaction potential, integrase inhibitor–based regimens have become more commonly recommended as preferred first-line options in many settings.

Safety, tolerability, and considerations: Neuropsychiatric adverse effects, including dizziness, insomnia, vivid dreams, and mood changes, are common with efavirenz and may persist in some patients. Other risks include rash, hepatotoxicity, and potential teratogenic effects in early pregnancy. Efavirenz interacts with many drugs and can affect hormonal contraception; careful assessment of concomitant medications is required. Pregnancy should be planned or managed with alternative regimens when possible.

Monitoring and resistance: As with all ART, adherence is crucial to prevent resistance. Viral load and CD4 count monitoring follow standard HIV treatment guidelines, with attention to any signs of intolerance or drug interactions.