Viranz Mechanism of Action

Pharmacology: Pharmacodynamics: Efavirenz is a selective non-nucleoside reverse transcriptase inhibitor (NNRTI) of human immunodeficiency virus type 1 (HIV-1). Efavirenz is a non-competitive inhibitor of HIV-1 reverse transcriptase (RT) with respect to template, primer or nucleoside triphosphates, with a small component of competitive inhibition. HIV-2 RT and human cellular DNA polymerases alpha, beta, gama and omega are not inhibited by concentrations of efavirenz well in excess of those achieved clinically.
Pharmacokinetics: Metabolism: Efavirenz has been shown to induce P450 enzymes, resulting in the induction of its own metabolism. The degree of CYP3A4 induction is expected to be similar between a 400 mg and 600 mg dose of efavirenz based on pharmacokinetic interaction studies in which daily 400 mg or 600 mg efavirenz doses in combination with indinavir did not appear to cause any further reduction of indinavir compared to a 200 mg dose of efavirenz.
Elimination: Efavirenz has a relatively long terminal half-life of 52 to 76 hours after single doses and 40 - 55 hours after multiple doses. Approximately 14 - 34% of a radiolabelled dose of efavirenz was recovered in the urine and less than 1% of the dose was excreted in urine as unchanged efavirenz.