A double-blind comparison of the long-term efficacy of a potassium channel opener and a calcium antagonist in stable angina pectoris

The efficacies and safety of nicorandil, 20 mg b.d., and diltiazem, 60 mg t.d., in the treatment of stable angina pectoris were compared in a double-blind randomized parallel group study involving 123 patients. The duration of the study was 3 months. Exercise tolerance tests were performed by the patients when on placebo (day 0) and at the end of the study period (day 90). Both groups were comparable at day 0 in terms of demography and cardiovascular status. Nicorandil and diltiazemwere both found to decrease the frequency of anginal attacks and the consumption of nitroglycerin tablets (P<0-01). Maximum exercise capacity, the amount of work that could be performed before reaching ischaemic threshold, and the amount of work required to reach onset of angina were significantly increased for both groups of patients on day 90 compared with day 0 (increase in maximum exercise capacity: nicorandil–6.9±18.9 kJ, diltiazem –9.6±16.2 kJ, P = 0.44ns; increase in work to ischaemic threshold: nicorandil–9.4±18.1 kJ, diltiazem–14.7±15.4 kJ, P = 0.10ns; increase in work to onset of angina: nicorandil–100±20.1 kJ, diltiazem–11.4±14.9 kJ, P = 0.68 ns). Differences between the two groups were not significant. The double product of systolic blood pressure × heart rate and peak exercise for both drugs was either unchanged or slightly decreased at ischaemic threshold. Approximately the same number of patients in each group experienced at least one adverse event (nicorandil;–32.7% diltiazem, –30.2%) and an equal number of the patients in each group withdrew from the study because of insufficient efficacy. At the end of the 3 month study it was decided to continue treatment (under double-blind conditions) for 1 year in an equal number of patients in each group (nicorandil, 45%, diltiazem, 43%). This indirectly reflected the investigators judgement of the risk/benefit ratio. These results indicate that the efficacy and safety profile of nicorandil, 20 mg b.d., is comparable with that of diltiazem, 60 mg t.d.