UBC Theses and Dissertations
A systematic review of the blood pressure lowering efficacy of calcium channel blockers in the treatment of primary hypertension Wong, Michelle Mon Yee
Context - Calcium channel blockers (CCBs) are widely used drugs to lower elevated blood pressure and manage angina and arrhythmias. Although the goal of antihypertensive therapy is to lower the risk of cardiovascular disease-related morbidity and mortality, efficacy is most often gauged by blood pressure reduction. Objectives — This systematic review of the blood pressure lowering efficacy of CCBs aims to determine the dose-related changes in systolic blood pressure (SBP), diastolic blood pressure (DBP), heart rate, and withdrawals due to adverse events (WDAE) with CCB treatment compared with placebo for a duration of 3-12 weeks, in patients with primary hypertension (SBP [greater than or equal to] 140 mm Hg and/or DBP [greater than or equal to] 90 mm Hg). Design — A systematic review, as per the methodology of the Cochrane Collaboration, of randomized placebo-controlled trials. Methods - Electronic databases were searched using a modified, expanded version of the search strategy used by the Cochrane Hypertension Review Group. RevMan 4.2 software was used to analyze data. Participants — 106 trials were included and reported data on 13 878 patients with a mean age of 55 years, mean baseline blood pressure of 158.2/101.6 mm Hg, mean pulse pressure of 56.7 mm Hg, and mean treatment duration of 5.7 weeks. Results — Maximal blood pressure lowering efficacy of CCBs is achieved at twice the manufacturer's recommended starting doses. This maximal reduction is 10/7 mmHg for dihydropyridines and 8/6 mmHg for non-dihydropyridines and likely represents an overestimate of the true blood pressure lowering effect due to publication bias. Combined, dihydropyridines and non-dihydropyridines lower pulse pressure by 3 mm Hg (95% CI: -4, - 2). Compared with placebo, WDAE increased in a dose-related fashion for dihydropyridines [relative risk of 1.8 (95% CI 1.2, 2.6) at 2 times the starting dose compared with 3.9 (95% CI: 2.2, 7.0) at 4 times the starting dose]. There were insufficient data to make a conclusion about the effect of non-dihydropyridines on WDAE. Conclusion — Dihydropyridines reduce blood pressure to a greater degree than nondihydropyridines. Maximal blood pressure lowering for both subclasses occurs with twice the manufacturer-recommended starting dose. Increasing the doses of dihydropyridines above recommended starting doses increases withdrawals due to adverse effects.
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