Slow release nifedipine plus atenolol in chronic stable angina pectoris.

1. The effects of adding slow release nifedipine in doses of 20 mg and 40 mg twice daily to atenolol therapy (50 mg twice daily) were assessed in 18 patients with chronic stable angina. 2. The addition of the lower dose of nifedipine to atenolol did not significantly alter the weekly consumption of glyceryl trinitrate or the mean number of anginal attacks as assessed by diary cards. However, 2 h after dosing there was a significant prolongation during stress testing in the time to onset of both 1 mm ST depression on the ECG (by 28%) and to angina (by 37%) compared with atenolol alone, but no benefit was apparent by 12 h after dosing. 3. At a dose of 40 mg twice daily, nifedipine significantly reduced glyceryl trinitrate consumption by 25% and the number of anginal attacks by 36%. The times to onset of ST depression and angina were increased by 37% and 55% respectively at 2 h and by 24% and 26% respectively 12 h after dosing. 4. Analysis of the frequency distribution of anginal attacks showed decreasing efficacy with time after administration of nifedipine. The overall results also suggest a relationship between efficacy and the plasma nifedipine concentration, with a mean 20% improvement in time to development of angina occurring at a nifedipine plasma concentration of approximately 30-40 ng ml-1. 5. In conclusion, the reduction of effort-related angina by nifedipine is related to its plasma concentration and the effective duration of action of the 20 mg slow release formulation is less than 12 h.