The use of labetalol in Japan: results of multicentre clinical trials.

1 The anti-hypertensive effects and safety of labetalol have been evaluated in multicentre clinical trials in Japan based on unified study protocols. The results of three studies are reported. 2 A total of 178 patients with essential hypertension were treated with labetalol for 12 weeks, 127 of them with labetalol alone (monotherapy) and the other 51 with labetalol plus diuretics (combined therapy). 3 Satisfactory antihypertensive effects were achieved in 76 of the 119 assessable patients in the monotherapy group and 25 of the 49 in the combined therapy group. The mean daily doses of labetalol were 329 mg in the monotherapy group and 374 mg in the combined therapy group. Seven patients (six in the monotherapy group; one in the combined therapy group) were withdrawn from the trials due to side-effects. 4 Sixty-one patients with hypertension were treated with labetalol alone or combined with diuretics for 6 months or longer. In most of these patients, good blood pressure control was achieved. No patients had to discontinue the treatment due to side-effects. The mean daily doses of labetalol were stabilised in and after week 8 of the treatment at an average of 260 mg in the monotherapy and 450 mg in the combined therapy. Tolerance to the anti-hypertensive effect did not develop. 5 Thirty patients with phaeochromocytoma were treated with labetalol and good blood pressure control was achieved in 21 of them. The effects of labetalol were better in patients with predominantly adrenaline-secreting tumours, and better in patients with sustained hypertensive type than in those with paroxysmal hypertensive type.