Steady-state nevirapine plasma concentrations are influenced by pregnancy

Objectives: Optimal plasma concentrations of antiretroviral drugs are required during pregnancy to treat maternal HIV infection and prevent mother-to-child transmission. We investigated the effect of pregnancy on nevirapine (NVP) plasma concentrations. Methods: We included all HIV-1-infected women for whom NVP plasma concentrations were available as part of routine patient care at two university hospitals. Plasma NVP concentrations were compared for pregnant (n = 45) and non-pregnant (n = 152) women. Univariate and multivariate linear regression analyses were used to identify and adjust for other confounding factors associated with NVP plasma concentrations. For pregnant women who had a plasma NVP concentration available both during and outside pregnancy, a paired analysis was performed. Results: Steady-state NVP plasma concentrations were lower in pregnant women: 5.2mg/L (interquartile range 3.9-6.8) vs. 5.8mg/L (4.3-7.7) (P = 0.08). After adjusting for confounders, both pregnancy (regression coefficient = -0.90mg/L, P = 0.046) and African descent (regression coefficient = +1.13mg/L, P = 0.005) influenced NVP concentrations significantly. The paired analysis showed mean concentrations of 4.8mg/L during pregnancy and 5.8mg/L outside pregnancy (paired t-test, P = 0.073). Conclusions: Pregnancy has a moderate but significant lowering effect on NVP plasma concentrations. Being of African descent compensates for the lowering effect of pregnancy on NVP concentrations.

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