David J. Cennimo, MD
Potential Financial Conflicts of Interest:Grants received: Bristol-Myers Squibb.
Cennimo DJ. Pharmacogenetics of Efavirenz: Adherence and Virologic Outcomes. Ann Intern Med. 2007;147:817. doi: 10.7326/0003-4819-147-11-200712040-00026
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Published: Ann Intern Med. 2007;147(11):817.
TO THE EDITOR:
Nachega and colleagues (1) describe the virologic response to nonnucleoside reverse transcriptase inhibitor (NNRTI) use across a spectrum of adherence in a predominantly (96.9%) black, South African patient cohort. Their findings suggest a superiority of efavirenz-based regimens over nevirapine even after adjustment for adherence and other baseline variables. One potential confounding variable is the delayed hepatic clearance of efavirenz noted in some U.S. patients of African descent (2). This has been attributed to mutation in the CPY2B6 gene (516G>T), which can prolong the efavirenz half-life to 48 hours in persons with TT homozygous mutations. In comparison, the half-lives in GG homozygotes and GT heterozygotes are 23 hours and 27 hours, respectively (3). This prolonged half-life, if present, could have ameliorated the effects of inconsistent adherence by maintaining effective levels until the next dose was taken. If this is the case, these effects may not be seen in alternate patient populations.
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