Indomethacin PK and PD Therapy in Pregnancy

Opportunistic study of indomethacin prescribed to patients per standard of care. Determine the pharmacokinetics, pharmacodynamics and pharmacogenomics of Indomethacin in pregnant patients with the hypothesis that that estradiol levels during pregnancy (12-32 weeks of gestation) and CYP2C9 polymorphisms affect the PK of indomethacin, and subsequently, the response to indomethacin therapy in patients at risk of Preterm birth (PTB). This hypothesis will be tested with the following specific aims: (1) Determine the PK of indomethacin in pregnant women at risk of PTB and its PD effects on reducing the rate of PTB before 34 weeks of gestation, as well as any associations between the PK and secondary maternal/neonatal clinical outcomes; (2) Determine the effects of maternal levels of estradiol in mid-pregnancy and CYP2C9 polymorphisms on indomethacin biotransformation to O-desmethylindomethacin in pregnant patients; (3) Construct a population PK/PD model of indomethacin in patients at risk of PTB (12-32 weeks of gestation) in order to optimize the dose and the dosing frequency for indomethacin prescribed to each individual based on covariates such as race/ethnicity, CYP2C9 genotype, gestational age, estradiol levels, smoking status, and body mass index (BMI). The investigators will enroll 300 subjects with spontaneous preterm labor (sPTL) or shortened cervix in a prospective opportunistic PK study designed to correlate the PK of indomethacin, patient genotype, and clinical outcomes. The investigators will merge dosing, sampling, demographic, and clinical information with the drug concentration data and use population PK methodologies to analyze the data using nonlinear mixed effect modeling. Quantification of the differences within and between individuals allows for identification of covariates (e.g., CYP2C9 genotype, estradiol levels, BMI, etc.) that can explain variability and affect drug exposure. These covariates, if significant, can then be used in the future to optimize dosing in individual patients at risk for PTB. Achieving this goal of individualized indomethacin therapy could have a significant impact on clinical practice and improve maternal and neonatal outcomes.

Inclusion criteria

To be enrolled in the study, patients must meet all of the following criteria:

• Age at least 18 years
• Singleton gestation
• 12 0/7 to 32 0/7 weeks gestation (see Gestational Age Determination section 3.2.1.1)
• Patient receiving indomethacin for any of the following diagnoses:

• Preterm labor: regular uterine contractions with documented cervical change or dilatation ≥ 2 cm and 80% effacement
• Cervical shortening (< 2.5 cm documented on transvaginal ultrasound) with or without funneling membranes
• Planned cervical cerclage or emergent cerclage
• Other condition whereby Indomethacin is indicated
• Maternal and fetal condition allows anticipated delay of delivery for more than 24 hours -

Exclusion criteria

• Exclusion criteria include:

• Contraindications to indomethacin use (history of maternal bleeding disorder, thrombocytopenia, maternal hepatic, gastrointestinal ulcerative, or renal dysfunction, asthma)
• Known fetal abnormality, genetic syndrome, or intrauterine fetal demise
• Anticipated delivery in less than 24 hours, cervical dilatation > 6 cm
• Preterm premature rupture of membranes
• Suspected chorioamnionitis
• Oligohydramnios (DVP < 2 cm)
• Congenital Uterine anomaly
• Vaginal bleeding due to suspected placental abruption or placenta previa
• Planned preterm delivery for maternal/fetal indications
• Non-reassuring fetal status
• Planned delivery outside UTMB or participation in another intervention trial which may affect maternal or neonatal outcomes
• Unsure gestational age due to possibility of intrauterine growth restriction
• Hematocrit <28% (as determined by most recent result within 1 month of enrollment)
• Prisoners