Effect of Pregnancy on Emtricitabine Pharmacokinetics
Effect of Pregnancy on Emtricitabine Pharmacokinetics
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.
HIV-1-infected pregnant women commonly receive antiretroviral drugs. Combination antiretroviral regimens including nucleoside reverse transcriptase inhibitors (NRTIs) and either a protease inhibitor or a nonnucleoside reverse transcriptase inhibitor are recommended for pregnant women requiring antiretroviral therapy for their own health. In addition, women who do not meet criteria for treatment for their own health generally receive antiretrovirals for prevention of mother-to-child transmission of HIV-1 (HIV).
Physiological changes during pregnancy affect antiretroviral drug disposition and previous studies of antiretroviral pharmacology during pregnancy have shown reduced antenatal exposure for many antiretrovirals. Inadequate antiretroviral exposure during pregnancy may yield inadequate virological control, increasing the risk of developing drug resistance mutations and of transmitting HIV to the infant. Understanding placental transfer of antiretrovirals to the foetus is of critical importance, as such transfer may subject the foetus to both the benefit of protection against HIV infection and the risk of potential antiretroviral toxicity. Before any antiretroviral can be used safely and effectively in pregnancy, its pharmacology must be studied in pregnant women.
Emtricitabine, an oral, synthetic, cytidine analogue NRTI with potent activity against HIV-1, is frequently used in pregnancy. In nonpregnant adults, emtricitabine is well absorbed and has low protein binding, and the labelled dose of 200 mg once daily results in an average area under the concentration versus time curve (AUC) of 10.0 ± 3.1 mg h/L. This average is based on data from both women and men. In these studies, the pharmacokinetics of emtricitabine were similar in adult female and male patients, and the data were not presented separately for women and men. Emtricitabine is primarily eliminated unchanged in the urine, and its clearance is proportional to renal function. A minor portion of emtricitabine is metabolized by oxidation of the thiol moiety to form the 3'-sulfoxide diastereomers and conjugation with glucuronic acid to form 2'-O-glucuronide, with no significant metabolism by the cytochrome P450 enzyme system. While the pharmacokinetics and appropriate dosing of emtricitabine in nonpregnant, adult, HIV-1-infected patients are well defined, no data are available describing emtricitabine pharmacokinetics with chronic use during pregnancy.
The primary objectives of this study were to describe emtricitabine pharmacokinetics in HIV-infected pregnant women and to determine if the standard dose of emtricitabine produces equivalent drug exposure during pregnancy to that seen in: 1) historical data for nonpregnant adults; and 2) the same women in the study cohort during the postpartum period. We also sought to evaluate the transplacental passage of emtricitabine by comparing concentrations in cord blood and maternal blood.
Abstract and Introduction
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.
Introduction
HIV-1-infected pregnant women commonly receive antiretroviral drugs. Combination antiretroviral regimens including nucleoside reverse transcriptase inhibitors (NRTIs) and either a protease inhibitor or a nonnucleoside reverse transcriptase inhibitor are recommended for pregnant women requiring antiretroviral therapy for their own health. In addition, women who do not meet criteria for treatment for their own health generally receive antiretrovirals for prevention of mother-to-child transmission of HIV-1 (HIV).
Physiological changes during pregnancy affect antiretroviral drug disposition and previous studies of antiretroviral pharmacology during pregnancy have shown reduced antenatal exposure for many antiretrovirals. Inadequate antiretroviral exposure during pregnancy may yield inadequate virological control, increasing the risk of developing drug resistance mutations and of transmitting HIV to the infant. Understanding placental transfer of antiretrovirals to the foetus is of critical importance, as such transfer may subject the foetus to both the benefit of protection against HIV infection and the risk of potential antiretroviral toxicity. Before any antiretroviral can be used safely and effectively in pregnancy, its pharmacology must be studied in pregnant women.
Emtricitabine, an oral, synthetic, cytidine analogue NRTI with potent activity against HIV-1, is frequently used in pregnancy. In nonpregnant adults, emtricitabine is well absorbed and has low protein binding, and the labelled dose of 200 mg once daily results in an average area under the concentration versus time curve (AUC) of 10.0 ± 3.1 mg h/L. This average is based on data from both women and men. In these studies, the pharmacokinetics of emtricitabine were similar in adult female and male patients, and the data were not presented separately for women and men. Emtricitabine is primarily eliminated unchanged in the urine, and its clearance is proportional to renal function. A minor portion of emtricitabine is metabolized by oxidation of the thiol moiety to form the 3'-sulfoxide diastereomers and conjugation with glucuronic acid to form 2'-O-glucuronide, with no significant metabolism by the cytochrome P450 enzyme system. While the pharmacokinetics and appropriate dosing of emtricitabine in nonpregnant, adult, HIV-1-infected patients are well defined, no data are available describing emtricitabine pharmacokinetics with chronic use during pregnancy.
The primary objectives of this study were to describe emtricitabine pharmacokinetics in HIV-infected pregnant women and to determine if the standard dose of emtricitabine produces equivalent drug exposure during pregnancy to that seen in: 1) historical data for nonpregnant adults; and 2) the same women in the study cohort during the postpartum period. We also sought to evaluate the transplacental passage of emtricitabine by comparing concentrations in cord blood and maternal blood.