Therapeutic drug monitoring (TDM) of atazanavir in pregnancy

Methods In this prospective, open labelled study, pregnant HIVpositive women received ATV/r as part of their routine pre-natal care. Demographic and clinical data were collected, and ATV plasma concentrations [ATV] were determined in the first (T1) and/or second (T2) and/or third (T3) trimester using HPLC-MS/MS (LLQ = 0.05 μg/mL). Postpartum (PP) sampling was performed where applicable. Antepartum (AP) and PP PK parameters were compared using a One-way ANOVA (for independent data sets) and a paired t-test (for paired data). Summary of results From January 2007 31 women (25 black African) were enrolled in the study. All received ATV/r at standard dose of 1 tablet once daily (300/100 mg od). 10/31 women initiated ATV/r treatment during pregnancy. Median (range) gestation at initiation in these patients was 24 weeks (7-35). Median (range) baseline CD4 count was 393 cells/μL (153-869) and 17 patients had a baseline plasma viral load of < 50 copies/mL. [ATV] were determined in 10/31 (T1); 17/31 (T2); 27/31 (T3) and 21/31 (PP) patients. Time of TDM sampling and [ATV] (geometric mean; 95%CI) are given in the Table. 2/17 patients at T2, 2/27 (T3) and 2/21 at PP had concentrations <LLQ (suggesting non-adherence). [ATV] were lower AP relative to that observed at PP (Table 1). Equally, in a paired analysis of 17 patients (T3 vs. PP), [ATV] were significantly reduced at T3 (P=0.0005).