Study selection and description
An initial search yielded 396 articles, subsequently narrowed to 4 articles for full text review (Supporting Information Table S1). These 4 articles comprised of randomised control trials comparing CCB to other anti-hypertensives in women with HDP, and included Black women in their demographics. An overview of the included studies’ characteristics and primary outcomes is illustrated in Figure 1 included in online supplementary material.
However, 3 out of 4 articles did not publish treatment effect by race, and therefore could not be used to answer the review question. We established contact with authors from all 3 studies where race based outcomes were not published however they were unable to grant access to original trial data, and therefore a meta-analysis was not possible.
Scardo et al randomised pregnant patients admitted to the Medical University of South Carolina with hypertensive emergencies, defined as a sustained systolic blood pressure of > 170 mm Hg or diastolic blood pressure of >105 mm Hg, to receive either oral Nifedipine (CCB) and 50 millilitres of Sodium Chloride or intravenous Labetalol and oral placebo consisting of corn starch powder in a double-blind trial. Black pregnant women comprised 62 percent of the sample size.12 The primary outcome was the time interval required to achieve the therapeutic blood pressure goal of <160 mm Hg systolic and <100 mm Hg diastolic. Patients receiving oral Nifedipine more rapidly achieved the therapeutic blood pressure goal in 25.0+ 13.6 minutes (mean+ SD) as compared with 43.6+ 25.4 minutes in those receiving Labetalol (p= 0.002). They also demonstrated that the Nifedipine group required significantly fewer doses (1.5 + 0.5 vs 2.5 + 1.5; p< 0.001) to reach the target blood pressure.
Belfort et al conducted an unblinded, randomised, multicentre trial in which 1650 patients with severe pre-eclampsia, defined as elevated blood pressure (> 140/90 mm Hg) with >1 + proteinuria and presence of one or more of the following: symptoms of pre-eclampsia, deranged liver function tests, intrauterine growth restriction or oligohydramnios; or persistent blood pressure > 160/110 mm Hg with proteinuria in the absence of other features, were included. Patients were allocated to oral Nimodipine (CCB) or intravenous Magnesium Sulphate.13 Blood pressure control was one of this study’s secondary outcomes. Baseline blood pressures and overall blood pressure readings were similar in both groups, although the authors noted that the group that received Magnesium Sulphate required Hydralazine more frequently to achieve target blood pressure levels. In the first hour after drug administration, there was a higher reduction of mean arterial pressure in the Nimodipine group compared to the Magnesium Sulphate group (-8.2% vs -4.2%). Within three hours of drug administration, reduction in mean arterial pressure was maintained in the Nimodipine group at 8.3 percent whereas the Magnesium Sulphate group had a 7.2 percent decrease in this time frame. Black patients accounted for 42 percent of the study group.
Sharma et al conducted a prospective, unblinded, randomised control trial amongst postpartum women with persistent hypertension, defined as sustained systolic blood pressure > 150 mm Hg and diastolic blood pressure > 100 mm Hg.14 25 participants each were allocated to Labetalol versus extended release Nifedipine. Time elapsed prior to achieving blood pressure control was similar between both groups (36.6 hours with Labetalol vs 38.2 hours with Nifedipine; p=0.51). In this study, where 36 percent of the group were Black, both oral Labetalol and Oral extended release Nifedipine were effective for the treatment of post-partum hypertension. At 72 hours post-partum, mean systolic blood pressure recorded for the Labetalol group was 140 (+ 15) mm Hg (mean+ SD) vs 141 (+ 27) mm Hg in Nifedipine group (p=0.94) and mean diastolic blood pressures were measured at 89 (+ 4) mm Hg vs 87 (+ 13) mm Hg (p=0.70) in Labetalol and Nifedipine groups respectively. Although time to blood pressure control did not differ significantly between medication groups, Labetalol achieved control more often with the starting dose (76 percent with Labetalol vs 46 percent with Nifedipine; p=0.04) and with fewer minor side effects compared to Nifedipine (20 percent with Labetalol vs 48 percent with Nifedipine; p=0.04).
The remaining article by Webster et al was a multi-centre randomised control trial in the U.K., which compared the effectiveness of Labetalol and Nifedipine in the management of chronic hypertension in pregnancy.15This study comprised of 62 Black pregnant patients who accounted for 54 percent of the study population of 112 women. A pre-specified exploratory subgroup analysis of the impact of ethnicity on efficacy of each treatment did not show any significant difference in mean systolic or diastolic brachial blood pressure in Black women (systolic 0.5 mm Hg; −4 to 5 mm Hg; diastolic 0.1 mm Hg; −3 to 3 mm Hg). No difference in mean systolic blood pressure was seen between treatment groups in study participants (−0.4 mm Hg; −4 to 3 mm Hg), but a 4-mm Hg (−6.6 to −0.8 mm Hg; p=0.015) reduction in mean diastolic blood pressure was seen in the Labetalol arm in non-Black participants. The authors concluded that some variation in treatment effect by ethnicity was noted, with Labetalol having a greater effect on reducing diastolic blood pressure in non-Black women. Nifedipine was associated with reduced central aortic pressure however the study was not powered to calculate what the most effective anti-hypertensive treatment for Black women with HDP is.