Effect of formulation and route of administration on the distribution of 17-hydroxyprogesterone caproate in rats.

Weekly intramuscular (250 mg/week) or subcutaneous (275 mg/week) injections of 17-hydroxyprogesterone caproate (17-OHPC) is the only treatment option for the prevention of preterm birth in women with a prior history of preterm delivery.The objective of the current study was to determine the relative distribution of 17-OHPC in selected tissues in adult female SD rats after IM (oily formulation or solution), IV (solution), PO (solution), or intravaginal (suppository) administration.Plasma, uterus, adipose, and liver samples were collected at various times and analysed by LC-MS-MS.The highest concentrations of 17-OHPC were observed in the adipose tissue, after IM (oily formulation), and intravaginal administration.Substantial concentrations of 17-OHPC were also observed in the uterus after IM, intravaginal and IV administration.17-OHPC was not detected in the liver and in any of the tissues tested after PO administration.17-OHPC levels in plasma after intravaginal suppository administration were low despite substantial concentrations in the adipose and the uterus.The distribution of 17-OHPC depends on the formulation, the route of administration, and the sampling time.Low systemic concentrations and substantial distribution in the tissues of interest after intravaginal administration warrants future studies to evaluate the potential of the daily intravaginal route of administration of 17-OHPC.

Pregnancy Alters CYP- and UGT-Mediated Metabolism of Buprenorphine.

BACKGROUND: In the United States, drug addiction has become a nationwide health crisis. Recently, buprenorphine (BUP), a maintenance therapy approved by the Food and Drug Administration, has been increasingly used in pregnant women for the treatment of opioid use disorder. Pregnancy is associated with various anatomic and physiological changes, which may result in altered drug pharmacokinetics (PKs). Previously, we reported that dose-adjusted plasma concentrations of BUP are lower during pregnancy than after pregnancy. The mechanism(s) responsible for this difference has not yet been defined. Our study aimed to evaluate alterations in cytochromes P450 (CYP)- and uridine diphosphate glucunosyltransferases (UGT)-mediated metabolism of BUP during pregnancy to determine the mechanism(s) responsible for this observation. METHODS: Data from 2 clinical studies were included in the current analysis. Study 1 was a prospective, open-labeled, nonrandomized longitudinal BUP PK study in pregnant women with a singleton gestation, stabilized on twice-daily sublingual BUP opioid substitution therapy. Each subject participated in up to 3 studies during and after pregnancy (the second, third trimester, and postpartum). The design of study 2 was similar to study 1, with patients evaluated at different time points during the pregnancy (first, second-half of pregnancy), as well as during the postpartum period. In addition, the dosing frequency of BUP study 2 participants was not restricted to twice-daily dosing. At each study visit, blood samples were collected before a BUP dose, followed by multiple collection times (10-12) after the dose, for up to 12 hours or till the end of the dosing interval. Plasma concentrations of BUP and 3 metabolites were quantified using validated ultraperformance liquid chromatography-tandem mass spectrometric assays. RESULTS: In total, 19, 18, and 14 subjects completed the PK study during 1/2 trimester, third trimester, and postpartum, respectively. The AUC ratios of norbuprenorphine and norbuprenorphine glucuronide to buprenorphine, a measure of CYP3A mediated N-demethylation, were 1.89, 1.84, and 1.33 during the first and second, third trimesters, and postpartum, respectively. The AUC ratios of buprenorphine glucuronide to BUP, indicative of UGT activity, were 0.71, 2.07, and 0.3 at first/second trimesters, third trimester, and postpartum, respectively. Linear mixed-effect modeling analysis indicated that the AUC ratios of CYP- and UGT-mediated metabolism of BUP were significantly higher during pregnancy compared with postpartum. CONCLUSIONS: The CYP and UGT activities were significantly increased as determined by the metabolic ratios of BUP during pregnancy compared with the postpartum period. The increased UGT activity appeared to account for a substantial part of the observed change in metabolic activity during pregnancy. This is in agreement with the need for BUP dose increment in pregnant women to reach similar BUP exposure and therapeutic effect as in nonpregnant subjects.

Gestational changes in buprenorphine exposure: A physiologically-based pharmacokinetic analysis.

AIMS: Buprenorphine (BUP) is approved by the US Food and Drug Administration for the treatment of opioid addiction. The current dosing regimen of BUP in pregnant women is based on recommendations designed for nonpregnant adults. However, physiological changes during pregnancy may alter BUP exposure and efficacy. The objectives of this study were to develop a physiologically-based pharmacokinetic (PBPK) model for BUP in pregnant women, to predict changes in BUP exposure at different stages of pregnancy, and to demonstrate the utility of PBPK modelling in optimizing BUP pharmacotherapy during pregnancy. METHODS: A full PBPK model for BUP was initially built and validated in healthy subjects. A fetoplacental compartment was included as a combined compartment in this model to simulate pregnancy induced anatomical and physiological changes. Further, gestational changes in physiological parameters were incorporated in this model. The PBPK model predictions of BUP exposure in pregnancy and during the postpartum period were compared to published data from a prospective clinical study. RESULTS: The predicted BUP plasma concentration-time profiles in the virtual pregnant populations are consistent with the observed data in the 2nd and 3rd trimesters, and the postpartum period. The differences in the predicted means of dose normalized area under the plasma drug concentration-time curve up to 12 h, average concentration and maximum concentration were within ±25% of the corresponding observed means with the exception of average concentration in the 3rd trimester (-26.3%). CONCLUSION: PBPK model-based simulation may be a useful tool to optimize BUP pharmacotherapy during pregnancy, obviating the need to perform pharmacokinetic studies in each trimester and the postpartum period that normally require intensive blood sampling.

An evidence-based recommendation to increase the dosing frequency of buprenorphine during pregnancy.

BACKGROUND: Dose-adjusted plasma concentrations of buprenorphine are significantly decreased during pregnancy compared with the nonpregnant state. This observation suggests that pregnant women may need a higher dose of buprenorphine than nonpregnant individuals to maintain similar drug exposure (plasma concentrations over time after a dose). The current dosing recommendations for buprenorphine during pregnancy address the total daily dose of buprenorphine to be administered, but the frequency of dosing is not clearly addressed. Based on buprenorphine's long terminal half-life, once-daily or twice-daily dosing has generally been suggested. OBJECTIVE: The objective of the study was to assess the impact of dosing frequency on buprenorphine plasma concentration time course during pregnancy. STUDY DESIGN: We utilized 3 data sources to determine an optimal frequency for dosing of buprenorphine during pregnancy: data from a pharmacokinetic study of 14 pregnant and postpartum women on maintenance buprenorphine in a supervised clinical setting; data from pregnant women attending a buprenorphine clinic; and data from a physiologically based pharmacokinetic modeling of buprenorphine pharmacokinetics in nonpregnant subjects. RESULTS: Among the 14 women participating in the pharmacokinetic study during and after pregnancy, plasma concentrations of buprenorphine were <1 ng/mL (the theoretical concentration required to prevent withdrawal symptoms) for 50-80% of the 12 hour dosing interval while at steady state. Among 62 women followed up in a opioid agonist treatment program, in which dosing frequency is determined in part by patient preference, 10 (16%) were on once-daily dosing, 10 (16%) were on twice-daily dosing, 28 (45%) were on thrice-daily dosing, and 14 (23%) were on four-times-daily dosing. A physiologically based pharmacokinetic model in nonpregnant subjects demonstrated that dosing frequency has an impact on the duration over which the plasma concentrations are below a specified plasma concentration threshold. CONCLUSION: A more frequent dosing interval (ie, three-times-daily or four-times-daily dosing) may be required in pregnant women to sustain plasma concentrations above the threshold of 1 ng/mL to prevent withdrawal symptoms and to improve adherence.

Dose-adjusted plasma concentrations of sublingual buprenorphine are lower during than after pregnancy.

BACKGROUND: Buprenorphine is a Food and Drug Administration-approved maintenance therapy for opioid use disorders and is increasingly being used in pregnant women with opioid use disorders as an alternative to methadone. Dosing of buprenorphine in pregnant women is based on the regimen recommended for nonpregnant females and males. Limited data are available defining the pharmacokinetic properties of sublingual buprenorphine administered during pregnancy. OBJECTIVE: This study evaluated the impact of physiological changes associated with pregnancy on the pharmacokinetics of sublingual buprenorphine during and after pregnancy. STUDY DESIGN: Pregnant women (n = 13), between 180/7 and 376/7 weeks' singleton gestation, receiving sublingual buprenorphine twice daily for opioid use disorders were studied. Pharmacokinetic-2 studies were performed between 18 and 25 weeks (n = 7), pharmacokinetic-3 studies were performed between 31 and 37 weeks (n = 11), and pharmacokinetic-P was performed 4-18 weeks postpartum (n = 10). On the day of the study, blood was withdrawn prior to the daily morning dose of buprenorphine and at 0.25, 0.5, 0.75, 1, 1.5, 2, 4, 8, and 12 hours after the dose. Buprenorphine plasma concentrations were analyzed by liquid chromatography tandem mass spectrometric detection. All pharmacokinetic parameters were observed or estimated using Microsoft Excel. Statistical analyses were performed to identify significant changes in study participants' buprenorphine pharmacokinetic parameter estimates over the duration of the study. Univariate linear and generalized linear mixed models were used to investigate changes in these measures over time, some of which were log transformed for normality. RESULTS: Dose-normalized (plasma concentration per dose) buprenorphine plasma concentrations were significantly lower during pregnancy (pharmacokinetic-2 plus pharmacokinetic-3) than during the postpartum period (pharmacokinetic-P). Specific pharmacokinetic parameters (and level of significance) were as follows: the area under the buprenorphine plasma concentration-time curves (P < .003), maximum buprenorphine concentrations (P < .018), buprenorphine concentrations at 0 hour (P < .002), and buprenorphine concentrations at 12 hours (P < .001). None of these parameters differed significantly during pregnancy (ie, pharmacokinetic-2 vs pharmacokinetic-3). The time to maximum buprenorphine concentrations did not differ significantly between groups. CONCLUSION: The dose-normalized plasma concentrations during a dosing interval and the overall exposure of buprenorphine (area under the buprenorphine plasma concentration-time curves) are lower throughout pregnancy compared with the postpartum period. This indicates an increase in apparent clearance of buprenorphine during pregnancy. These data suggest that pregnant women may need a higher dose of sublingual buprenorphine compared with postpartum individuals. The dose of buprenorphine should be assessed after delivery to maintain similar buprenorphine exposure during the postpartum period.

Route of administration and formulation dependent pharmacokinetics of 17-hydroxyprogesterone caproate in rats.

1. Weekly intramuscular injections of (250 mg/week) of 17-hydroxyprogesterone caproate (17-OHPC) are the only treatment option for prevention of preterm birth in women with a prior history of preterm delivery. 2. The objective of the current study was to evaluate the use of an alternate formulation and the feasibility of an alternate route of administration of this agent. 17-OHPC was administered to adult female SD rats, as marketed oily formulation intramuscularly, or as a solution IV, IM, or PO. 3. Plasma concentrations of 17-OHPC were measured by LC-MS-MS and pharmacokinetic parameters were calculated by non-compartmental analysis, using WinNonLin (Certara, St. Louis, MO). 4. After IV or IM administration as a solution, the mean half-life of 17-OHPC was around 11 h. The bioavailability was nearly 100% after IM administration, but was very low (<3%) after PO administration of a solution dosage form. 5. Intramuscular injection of the oily formulation resulted in low levels of 17-OHPC that were sustained for a prolonged time period with a projected bioavailability close to 100%. 6. The pharmacokinetics of 17-OHPC is dependent on the formulation and the route of administration. 7. The low bioavailability after oral administration indicates that oral administration of 17-OHPC may not be feasible with simple formulations of this drug.