A randomized controlled trial comparing the efficacy of nifedipine and enalapril in the postpartum period

Abstract

Background: Postpartum hypertension is a common medical complication of pregnancy and is associated with increased healthcare use, including unplanned interactions with the medical system and readmission, which can add significant stress to both a newly postpartum patient and the medical care delivery system. We currently do not know what the best antihypertensive treatment for postpartum hypertension is and tend to use antihypertensives commonly used during pregnancy. However, the mechanism of action of angiotensin-converting enzyme inhibitors may be well suited for the pathophysiology of hypertension in the postpartum period and may help to provide better control of hypertension and, in turn, decrease healthcare use.

Objective: This study aimed to determine if enalapril is superior to nifedipine in preventing prolonged hospitalizations, unplanned medical visits, and/or readmission among women with postpartum hypertension.

Study design: We performed an open-label, randomized controlled trial (ClinicalTrials.gov registered: NCT04236258) in which patients ≥18 years with chronic hypertension, gestational hypertension, or preeclampsia were recruited to receive either 10 mg enalapril daily or 30 mg extended-release nifedipine daily as an initial antihypertensive agent in the period from delivery to 6 weeks postpartum. Recruitment occurred at a tertiary academic hospital from January 2020 to February 2021. Exclusion criteria included being on an antihypertensive when pregnancy started or requiring ≥2 daily antihypertensives during pregnancy. The antihypertensive regimen was managed by the participants' obstetrical provider after the initial randomization. The primary outcome was a composite of prolonged hospitalization, unplanned clinic visits, triage visits, and/or readmission. A total of 40 patients in each arm were needed to detect a decrease in the primary outcome rate from 70% to 40% (α=0.05; power 0.80). Analyses were performed based on the intention-to-treat principal, and each arm was oversampled because of the risk for participant dropout.

Results: A total of 47 patients were randomized to each arm. Aside from the mode of delivery and twin gestation, the maternal demographics were similar between the 2 groups. The primary outcome occurred in 31 of 47 patients (66%) randomized to the nifedipine group and in 30 of 47 (64%) randomized to the enalapril group (P=.83). There was no significant difference in the primary outcome after controlling for mode of delivery and twin gestation. More patients in the enalapril arm had a second antihypertensive added during their primary hospitalization (16 vs 6) and more patients in the nifedipine arm were still on their antihypertensive at 2 weeks postpartum (42 vs 36). There were no adverse events in either group.

Conclusion: Enalapril was not superior to nifedipine when used as an initial antihypertensive in the immediate postpartum period in terms of decreasing healthcare use.

Keywords: antihypertensive; enalapril; hypertension; nifedipine; postpartum; preeclampsia; readmission.