Emtricitabine: an antiretroviral agent for HIV infection.

Emtricitabine, a nucleoside reverse transcriptase inhibitor, is phosphorylated by cellular enzymes to emtricitabine 5'-triphosphate which, in turn, inhibits the activity of HIV-1 (HIV) reverse transcriptase by competing with the endogenous substrate. Incorporation of the triphosphate into the viral DNA causes chain termination, thereby inhibiting viral replication. In adult patients infected with HIV, combination therapy including emtricitabine 200 mg once daily was as effective as triple therapy including lamivudine 150 mg twice daily and significantly more effective than stavudine (at standard dosages) or protease inhibitor-based therapy at achieving and/or maintaining durable suppression of HIV levels after 24-48 weeks of therapy. In addition, 85% of emtricitabine recipients maintained virological success (<400 copies/mL) during 96 weeks of therapy. Triple therapy including emtricitabine 6 mg/kg once daily decreased (to <400 copies/mL) or maintained durable suppression of HIV RNA levels in approximate, equals 90% of children and adolescents (aged 13 months to 17 years) after 16-24 weeks of therapy. Emtricitabine-based therapy was generally well tolerated; most adverse events being mild to moderate in intensity. Emtricitabine-based regimens were as well tolerated as those with lamivudine, and better tolerated than those with stavudine.