Comparison of Dihydropyridine and Phenylalkylamine Calcium Antagonists in Patients with Coronary Heart Disease
To evaluate possible differences between dihydropyridine and phenylalkylamine calcium antagonists in the setting of chronic stable angina, 2 placebo-controlled, double-blind, crossover trials were conducted comparing the effects of gallopamil and nifedipine on exercise tolerance and ischaemic ST depression, using standard as well as slow release formulations.
In the first study, 30 patients received standard formulations of gallopamil (50mg 3 times daily) and nifedipine (20mg 3 times daily). This trial was stopped after 9 patients had been enrolled, because of severe exacerbation of angina in 3 nifedipine recipients. 21 patients then entered a second protocol in which the nifedipine dose was reduced to 10mg 3 times daily. Compared with the preceding placebo periods, time to angina onset and total exercise time were statistically significantly (p < 0.01) prolonged by gallopamil (by 30 and 18%, respectively), and nonsignificantly prolonged by nifedipine (by 20 and 13%, respectively), after 4 weeks’ treatment. Increases in heart rate and rate-pressure product at maximal comparable workloads were less with gallopamil than with nifedipine (p < 0.01). In contrast to nifedipine, gallopamil was associated with very few side effects. The second trial comprised 24 patients who received slow release formulations of gallopamil (100mg twice daily) and nifedipine (20mg twice daily) over 2 weeks. Again, both drugs exhibited significant anti-ischaemic efficacy, as evidenced by reductions in ST depression at maximal comparable workloads and increases in exercise time compared with placebo, but the differences between the treatments were not statistically significant. Side effects were more frequent with nifedipine, but less severe than with the standard formulation.
In standard formulation, gallopamil is preferable to nifedipine because of a marginally higher efficacy, fewer side effects and, therefore, a more favourable risk: benefit ratio. The usefulness of nifedipine is substantially limited by significant adverse reactions, probably due to excessive reflex sympathetic discharge. The use of slow release formulations appears to attenuate these differences without completely abolishing them.
KeywordsNifedipine Chronic Stable Angina Angina Onset Gallopamil Anginal Frequency
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