This double-blind, placebo-controlled, cross-over study was designed to evaluate the effects and duration of action of gallopamil sustained release (SR) in patients with stable effort angina. Exercise tests were performed 3, 8, and 12 hours after the last administration of placebo or gallopamil SR. Blood samples for plasma gallopamil concentration were taken just before each exercise test. Statistical analysis was performed using an analysis of variance for multiple comparisons with evaluation of interaction between sequence and period according to a cross-over design. Compared to placebo, gallopamil SR significantly prolonged exercise time from 412 +/- 100 to 481 +/- 71 s (p less than 0.02; 17%), from 416 +/- 88 to 484 +/- 67 s (p less than 0.01; 16%), and from 364 +/- 88 to 440 +/- 85 s (p less than 0.02; 21%) at 3, 8 and 12 hours respectively after administration. Time to -1 mm ST segment depression was also significantly prolonged from 263 +/- 56 to 336 +/- 76 s (p less than 0.001; 28%), from 262 +/- 81 to 356 +/- 70 s (p less than 0.001; 36%), from 231 +/- 65 to 291 +/- 76 s (p less than 0.001; 26%), respectively. No significant relationship between plasma levels and anti-ischemic activity was observed. In conclusion, our data show that gallopamil slow-release is effective in improving exercise tolerance of patients with chronic angina and that its therapeutic effect persists, substantially unchanged, up to 12 hours after administration.