The one-compartment analysis yielded similar emtricitabine exposure parameters to the noncompartmental analysis. A summary of the pharmacokinetic parameters from the noncompartmental analysis for emtricitabine antepartum and postpartum is provided in Table 2. Figure 3 depicts the median antepartum and postpartum concentration–time curves. Geometric mean (90% CI) emtricitabine pharmacokinetic parameters during the third trimester compared with postpartum, respectively, for AUC were 8.0 (7.1–8.9) mg h/L vs. 9.7 (8.6–10.9) mg h/L (P = 0.072), for CL/F were 25.0 (22.6–28.3) L/hr vs. 20.6 (18.4–23.2) L/hr (P = 0.025), and for 24 hour post dose concentration (C24)

were 0.058 (0.037–0.063) see more mg/L vs. 0.085 (0.070–0.010) mg/L (P = 0.006). All but one pregnant subject had C24 ≥0.037 mg/L,

well above the inhibitory concentration 50%, or drug concentration that suppresses viral replication by half (IC50) for emtricitabine of 0.004 mg/L and close to the IC90 of 0.051 mg/L. The lowest postpartum C24 was 0.07 mg/L, exceeding the IC90. One pregnant woman had a detectable pre-dose emtricitabine concentration, but had C24 below the limit Target Selective Inhibitor Library research buy of detection (< 0.0118 mg/L). Postpartum, four different women had pre-dose emtricitabine levels below the limit of detection but all had detectable emtricitabine concentrations at 24 hours post-dose. Umbilical cord blood samples were collected for 16 subjects; maternal plasma samples at delivery were available for 15 of the 16 subjects; emtricitabine was undetectable in three maternal and four cord blood samples. The geometric mean of the measurable maternal concentrations at delivery was 0.15 mg/L (90% tuclazepam CI 0.09–0.26 mg/L) and that of the cord blood concentrations was 0.26 mg/L (90% CI 0.17–0.39 mg/L).

The geometric mean ratio of cord/maternal concentrations in 11 paired subject samples with detectable concentrations was 1.2 (90% CI 1.0–1.5). The median time between the last dose of emtricitabine and delivery was 18.6 hours (range 2.7–50.0 hours). Overall, emtricitabine was well tolerated during pregnancy and postpartum, with only three subjects experiencing grade 3 adverse events of elevated bilirubin while taking emtricitabine. All three of these subjects were concomitantly taking atazanavir, which is known to cause hyperbilirubinaemia. Of the four subjects who discontinued emtricitabine prior to the postpartum pharmacokinetic evaluation, none indicated side effects of emtricitabine as a reason for discontinuation. Twenty-four subjects had viral loads <400 HIV-1 RNA copies/mL at delivery; viral loads were missing in two subjects. At the postpartum evaluation, viral loads were < 400 copies/mL in 15 women, were ≥400 copies/mL in four women, and were not obtained in seven women.

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