Prophylactic effect of intravenous tiapamil on methylergometrine-induced coronary artery spasm in patients with variant angina: randomized double-blind trial.

Tiapamil is a new calcium entry blocker. The ability of its intravenous form to prevent methylergometrine-induced coronary artery spasm was studied in 11 consecutive patients with angiographically documented vasospastic angina. The study was designed as a double-blind crossover trial of tiapamil vs placebo. Each patient received, in a randomized order, either tiapamil, as a 1.5 mg/kg intravenous bolus followed by a 50 micrograms/kg/min infusion lasting 3 hours, or a matched placebo. Immediately after the infusion, methylergometrine tests were performed with up to 0.4 mg of methylergometrine or until a positive ECG was recorded. Compared to the values obtained after placebo infusion, tiapamil significantly lowered systolic and diastolic blood pressure (respective pre- and posttiapamil values: 119.9 +/- 17.7 vs 142.1 +/- 25.5 mm Hg, p less than 0.01; and 72.0 +/- 9.1 vs 82.4 +/- 9.3 mm Hg, p less than 0.02); the drug exerted no significant effect on heart rate (63.9 +/- 13.3 vs 67.6 +/- 16.5 bpm, NS), PR interval (0.180 +/- 0.020 vs 0.177 +/- 0.017 sec NS), or QTc interval (404.4 +/- 16.5 vs 396.0 +/- 26.6 msec, NS). After placebo, 10 patients had positive methylergometrine tests following single doses ranging from 0.1 to 0.4 mg. The remaining patient developed ventricular bigeminy, which resolved immediately after administration of isosorbide dinitrate; his test was therefore considered negative in the evaluation of the results. In contrast, after tiapamil, eight patients had negative tests for doses of up to 0.4 mg methylergometrine, and three had positive tests for the same methylergometrine doses as after the placebo.(ABSTRACT TRUNCATED AT 250 WORDS)