Background:  Pregnancy can alter the pharmacokinetics of several protease inhibitors, potentially requiring dose adjustment. Our aim was to describe atazanavir/ritonavir (ATV/r) pharmacokinetics before and after delivery.

Methods:  An intensive steady-state 24-hour pharmacokinetic profiles of ATV/r given once daily (with zidovudine [AZT]/lamivudine [3TC] twice daily) in the third trimester of pregnancy and at least 4 weeks postpartum was carried out. Paired maternal and umbilical cord blood samples were collected at delivery. ATV concentrations were measured by a validated high-performance liquid chromatography (HPLC) method (limit of quantification 20 ng/µL).

Results:  A total of 31 women (17 previously described, 52% white) completed the ante/postpartum evaluations. Mean age (±SD) was 29 (5) years, median (IQR) baseline CD4 count was 413 (354 to 616) cells/µL, median (IQR) viral load was 8357 (1057 to 16,200) copies/µL for patients with detectable viremia. In pre- and postpartum evaluations (see the figure), respectively, the pharmacokinetic parameters were as follows:  ATV GM AUC 0 to 24 (range) was 29,848 (7477 to 74,008) vs 32,389 (10,229 to 71,971) ng*h/mL (P = 0.48), the ATV GM C_max (range) was 2680 (636 to 6128) vs 3070 (683 to 10,412) ng/µL, (P = 0.13), and the ATV GM C 24 h (range) was 439 (109 to 989) vs 405 (25 to 1944) ng/µL (P = 0.18). Median T_max (IQR) was 3 (2 to 4) vs 2 (2 to 3) hours. The mean (±SD) ATV fetal/maternal ratio was 0.14 (0.07). One baby required phototherapy for 2 days and all tested HIV RNA negative at 1-year follow-up.

Conclusions:  Dose adjustment for ATV/r is not required during pregnancy as ATV pharmacokinetic profiles are similar during third trimester and postpartum. Trans-placental passage of ATV was confirmed to be low.