Duration of action of tiapamil in stable exercise induced angina

The duration of action of tiapamil was assessed in ten patients with stable exertional angina. Maximal symptom-limited treadmill exercise electrocardiography was performed before and at 1, 3, 6 and 9 h after therapy. Significant differences were only found at 1 h after tiapamil with increases in mean exercise duration (312 vs 399 s), the time to onset of angina (221 vs 310 s) and exercise work load (5.9 vs 7.3 METS). Tiapamil had no significant effect on the exercise heart rate but increased the resting heart rate by 6 beats/minute. The resting systolic blood pressure fell by 17 mmHg (p less than 0.01), and the diastolic blood pressure by 14 mmHg. Exercise systolic and diastolic blood pressures fell by 19 and 17 mmHg respectively. Side-effects were short-lived and attributable to vasodilatation. Tiapamil is effective for the relief of angina with minimal side-effects, but its duration of action is short. For effective chronic oral use, a sustained release preparation is required.