Effect of pregnancy on emtricitabine pharmacokinetics

Abstract

Objectives The aim of the study was to describe emtricitabine pharmacokinetics during pregnancy and postpartum. Methods The International Maternal Pediatric and Adolescent AIDS Clinical Trials (IMPAACT), formerly Pediatric AIDS Clinical Trials Group (PACTG), study P1026s is a prospective pharmacokinetic study of HIV-infected pregnant women taking antiretrovirals for clinical indications, including a cohort taking emtricitabine 200 mg once daily. Intensive steady-state 24-hour emtricitabine pharmacokinetic profiles were performed during the third trimester and 6–12 weeks postpartum, and on maternal and umbilical cord blood samples collected at delivery. Emtricitabine was measured by liquid chromatography–mass spectrometry with a quantification limit of 0.0118 mg/L. The target emtricitabine area under the concentration versus time curve, from time 0 to 24 hours post dose (AUC0-24), was ≥7 mg h/L (≤30% reduction from the typical AUC of 10 mg h/L in nonpregnant historical controls). Third-trimester and postpartum pharmacokinetics were compared within subjects. Results Twenty-six women had pharmacokinetics assessed during the third trimester (median 35 weeks of gestation) and 22 postpartum (median 8 weeks postpartum). Mean [90% confidence interval (CI)] emtricitabine pharmacokinetic parameters during the third trimester vs. postpartum were, respectively: AUC: 8.0 (7.1–8.9) vs. 9.7 (8.6–10.9) mg h/L (P = 0.072); apparent clearance (CL/F): 25.0 (22.6–28.3) vs. 20.6 (18.4–23.2) L/h (P = 0.025); 24 hour post dose concentration (C24): 0.058 (0.037–0.063) vs. 0.085 (0.070–0.010) mg/L (P = 0.006). The mean cord:maternal ratio was 1.2 (90% CI 1.0–1.5). The viral load was <400 HIV-1 RNA copies/mL in 24 of 26 women in the third trimester, in 24 of 26 at delivery, and in 15 of 19 postpartum. Within-subject comparisons demonstrated significantly higher CL/F and significantly lower C24 during pregnancy; however, the C24 was well above the inhibitory concentration 50%, or drug concentration that suppresses viral replication by half (IC50) in all subjects. Conclusions While we found higher emtricitabine CL/F and lower C24 and AUC during pregnancy compared with postpartum, these changes were not sufficiently large to warrant dose adjustment during pregnancy. Umbilical cord blood concentrations were similar to maternal concentrations.

Protecting the Fetus Against HIV Infection: A Systematic Review of Placental Transfer of Antiretrovirals

“…The observed ratio was lower for didanosine, at 0.38, but only included a single study with 10 patients [7]. Of the three emtricitabine studies, the geometric mean ratio of cord to maternal plasma concentration was 1.2 in one study (n = 11); for this study the median time between dosing and delivery was 19 hours [13]. For the other emtricitabine study (n = 10), the median cord to maternal ratio was 1.6 but the median time between dosing and delivery was 8.5 hours [14].…”

Pregnancy-Associated Changes in Pharmacokinetics: A Systematic Review

“…This collection of PK data could prove to be a decision support base for future attempts to tailor medication prescription for pregnant women to achieve target serum concentrations; however, one must take into account that many studies often report undiminished drug efficacy despite the aforementioned pregnancy-associated PK changes [132,135,138,145,146,163,172,177]. …”

Alteration in cytochrome P450 3A4 activity as measured by a urine cortisol assay in HIV‐1‐infected pregnant women and relationship to antiretroviral pharmacokinetics

“…Determination of the 6βHF : F urinary ratio was carried out on the same days as the pharmacokinetic evaluations. Results of the pharmacokinetic evaluations for ABC, FTC, LPV/r, NFV, NVP and TFV have been previously reported .…”