Calcium Channel Blocker Therapy in Black Hypertensive Patients

To the Editor: In their recent paper titled “Racial Differences in Blood Pressure Response to Calcium Channel Blocker Monotherapy: A Meta-Analysis,” Nguyen et al. reviewed the existing evidence on ethnic differences in efficacy of calcium channel blocker therapy for hypertension.1 The research question was whether black hypertensive people have a differential response to calcium channel blockers as compared to white people. With six eligible studies, four in blacks vs. whites, the result of the meta-analysis was that the pooled difference in mean systolic and diastolic blood pressure between blacks and whites was, respectively, −2.7 mm Hg (95% confidence interval (CI) −4.0 to −1.3) and −0.4 mm Hg (95% CI −1.0 to 0.3), with greater responses in black people. Furthermore, with the use of calcium channel blockers, whites were as likely as blacks to attain the diastolic blood pressure goal of <90 mm Hg or a 10 mm Hg or greater change (relative risk 1.00; 95% CI 0.91–1.11). These results are in line with a larger review on ethnic differences in response to different classes of antihypertensive drugs.2 The authors concluded that blood pressure reduction to calcium channel blockers is similar in US blacks and whites, and suggest that race is not likely to offer any clinical utility for decisions about the effect of calcium channel blockers. However, Nguyen et al. did not include trials in black people only, did not provide information on blood pressure levels at inclusion, nor on blood pressure levels used for exclusion during the trial, on drop outs, or on whether the trials provided per protocol or intention-to-treat analysis. This is important, as excluding trials conducted in black people only, might create biased review results.3 In addition, patients with higher blood pressure levels or with resistance to treatment are often excluded before randomization, or during the trial, while there is a more frequent occurrence of severe, resistant hypertension in the black population, which progresses more rapidly to morbidity and mortality.3,4 The papers included in the review by Nguyen et al. We retrieved, mainly considered patients with diastolic blood pressure <110 mm Hg. But evidence indicates that when all randomized-controlled antihypertensive drug trials in black patients are reviewed, with details provided on blood pressure at study entry and drop outs, calcium channel blockers are the only drug type that effectively lowers blood pressure across all subgroups of black patients. This includes patients with a baseline diastolic blood pressure ≥110 mm Hg.3 These aggregated data should be utilized to treat black hypertensive patients, regardless of the drug effects in whites or other ethnic groups. Ethnic differences in the response to antihypertensive drugs may provide important clues to the pathophysiology of hypertension and the mode of action of the drugs. But when treating black hypertensives the evidence needed by the clinician is which antihypertensive drug is most effective in black patients, rather than how other ethnic subgroups might have responded to the therapy.