A comparative study of once-daily amlodipine versus twice-daily diltiazem controlled release (CR) in the treatment of stable angina pectoris. Amlodipine Study Group.

A multicenter, double-blind study was performed to compare the efficacy and safety of the calcium antagonists, amlodipine and diltiazem controlled release (CR), in patients with stable angina pectoris. One hundred and thirty-two patients were randomized to receive either amlodipine (5-10 mg) once daily or diltiazem CR (90-120 mg) twice daily for 8 weeks. A standard bicycle exercise tolerance test was used for the primary efficacy assessment. The median time to 1 mm ST-segment depression and time to onset of chest pain were increased by 16% (P < 0.0001) and 13% (P < 0.0001) with amlodipine, and by 16% (P < 0.0001) and 7% (P = 0.009) with diltiazem CR, respectively. Amlodipine, but not diltiazem CR, also produced a significant improvement in the median time to end of exercise of 5% (P < 0.0002), although the between-treatment difference for this parameter was not statistically significant. The number of angina attacks and nitroglycerin (NTG) tablet consumption were similar with both agents. Amlodipine was withdrawn in 3% and diltiazem CR in 9% of patients due to adverse events. The adverse events were reported by 15% of patients on amlodipine and 26% of those on diltiazem CR. The results from this study demonstrate that both drugs have a comparable therapeutic effect and possibly that amlodipine was better tolerated in patients with stable angina. Furthermore, amlodipine has the advantage of once-daily dosing and so may also be beneficial in ensuring good patient compliance.