Pharmacoepidemiology
Comparative effectiveness of oral antihypertensives initiation during pregnancy in a California Medicaid population, 2016-2020. Catherine Psaras* Catherine Psaras Psaras Psaras Psaras University of California, San Diego
To extend findings from the Chronic Hypertension and Pregnancy (CHAP) trial, we compared initiation of labetalol, nifedipine, and methyldopa by 23 weeks’ gestation among pregnant patients with chronic hypertension, focusing on effectiveness and safety. We used California Medicaid claims linked to the California Study of Mothers and Infants for deliveries from 2016-2020. Exposure was defined as at least one paid fill for labetalol, extended-release nifedipine, or methyldopa by 23 weeks’ gestation among patients with no oral antihypertensive use from 90 days before last menstrual period (LMP) through LMP. As in CHAP, the composite effectiveness outcome included preeclampsia with severe features, preterm birth <35 weeks, placental abruption, and fetal or neonatal death. Small for gestational age birth (SGA) was evaluated as a safety outcome. The cohort included 2,282 singleton births (1,496 labetalol, 653 methyldopa, 133 nifedipine). Composite outcome incidence differed modestly by medication (labetalol 23%, methyldopa 19%, nifedipine 25%). Compared with labetalol, methyldopa was associated with lower risk (adjusted risk ratio [aRR] 0.82; 95% CI 0.68-1.00), while nifedipine showed no difference (aRR 1.03; 95% CI 0.74-1.43). Nifedipine versus methyldopa yielded an aRR of 1.25 (95% CI 0.80-1.70). For SGA, results were similar (aRR (95% CI): methyldopa vs. labetalol: 0.81 (0.62, 1.05); nifedipine vs. labetalol: 1.06 (0.65, 1.74); nifedipine vs. methyldopa: 1.32 (0.62, 2.01)). Labetalol and nifedipine showed comparable effectiveness and safety, while methyldopa was associated with lower risks of adverse outcomes. Limited overlap between treatment groups and potential residual confounding warrant cautious interpretation. Further research is needed to determine whether the apparent advantage of methyldopa reflects a true therapeutic benefit or underlying bias.