An estimated 2.9 million people in sub-Saharan Africa and 0.6 million people in Asia were receiving antiretroviral therapy (ART) as of December 2008 [1]. More than 66% of ART regimens in these regions High Content Screening include the nonnucleoside reverse transcriptase inhibitor (NNRTI) nevirapine [1], which is highly effective [2], nonteratogenic [3,4] and has little long-term toxicity [5,6]. Nevirapine, however, can cause early hepatotoxicity [7,8] and rash [9], including potentially life-threatening hypersensitivity reactions [10]. Although the definition
of nevirapine-associated hepatotoxicity has been inconsistent in clinical studies, serious hepatotoxicity is usually defined in one of three ways: (i) an increase in serum alanine transferase (ALT) or aspartate transaminase (AST) to greater than or equal to five times the upper limit of normal (ULN) (severe hepatotoxicity), (ii) rash
associated with a 2.5-fold increase in ALT or AST above ULN (rash-associated hepatotoxicity), or (iii) fatal hepatotoxicity. A retrospective analysis of 633 women enrolled in 17 trials conducted by nevirapine’s original manufacturer, Boehringer-Ingelheim (Ingelheim, Germany), found that the risk of rash-associated hepatotoxicity was significantly greater (P<0.01) in women with a baseline CD4 count ≥250 cells/μL (11.0% compared with 0.9% among women with baseline CD4 count <250 cells/μL) [11–15]. These findings led the US Food and Drug Administration to issue a black box warning against treating women with CD4 counts ≥250 cells/μL with nevirapine unless the Wnt inhibitor benefits clearly outweigh the risks [11]. Some subsequent studies have supported this association [16] but other studies have not found an association between risk for hepatotoxicity and CD4 cell count [17–19]. In addition, a genetic basis for nevirapine-associated hepatotoxicity has been proposed [20], although it is unclear if a genetic predisposition could have confounded the CD4 count ≥250 cells/μL association reported in the Boehringer-Ingelheim
analysis. The 2006 World Health Organization (WHO) recommendations for initiating ART [21] have led to significant numbers of women in resource-limited settings starting ART (often nevirapine-based) at CD4 counts ≥250 cells/μL. For example, of 11 776 Zambian Methocarbamol adults initiating predominantly nevirapine-based ART from 2004 to 2005, 601 (5%) had a baseline CD4 count ≥350 cells/μL and 2097 (18%) had a baseline CD4 count of 200–350 cells/μL [22]. In addition, the new 2009 WHO recommendations which recommend starting ART in all patients with a CD4 count <350 cells/μL will further increase the number of women starting nevirapine-based ART at a CD4 count ≥250 cells/μL [23]. Despite the large numbers of women being treated with nevirapine-based ART, few studies have evaluated the risk of hepatotoxicity among women with CD4 counts ≥250 cells/μL in resource-limited settings.
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