Effect of dipyridamole at the usual oral dose on exercise-induced myocardial ischemia in stable angina pectoris

Abstract A randomized, double-blind, placebo-controlled study was performed to investigate the effect of dipyridamole at a usual oral dose of 150 mg/day on 18 patients with angina pectoris and positive treadmill exercise electrocardiography. After their angina pectoris was stabilized in phase 1, the patients were randomly assigned to sequence group A or B. Group A received a placebo 3 times daily in phase 2 and then 50 mg of dipyridamole 3 times daily in phase 3. Group B received the treatment in the reverse order. The degree of ST depression and the threshold for angina pectoris in treadmill exercise electrocardiography, which was performed on the last days of phases 2 and 3, were compared. The mean duration of exercise was 5 minutes and 23 seconds during dipyridamole and 5 minutes and 13 seconds during placebo administration, with no significant difference. Dipyridamole caused an aggravating effect on the ST change (earlier appearance of ST depression and/or deeper total sum of ST depression at the end of the exercise) in 3 patients, a salutary effect in 5 and no effect in 10. Dipyridamole decreased the threshold for angina pectoris in 5 patients, increased it in 6 and did not change it in 7. To summarize, dipyridamole showed adverse effects (aggravative effects on the ST change and/or on the threshold for angina pectoris) in 6 patients, beneficial effects in 8 and no effect in 4. A usual oral dose of dipyridamole induced myocardial ischemia during exercise in some patients while it improved it in a similar number of patients.