Antihypertensive effect of carvedilol: a preliminary dose-response study.

The blood pressure (BP) lowering effect of low doses of antihypertensive agents is not usually explored because of the difficulty in detecting small changes in BP. Since ambulatory blood pressure monitoring in a cross-over trial design can reliably detect differences of 5 mmHg with less than 20 subjects, we have used this technique to assess the dose-response curve of a new beta-blocker, carvedilol. Twenty subjects were enrolled after diagnostic ambulatory BP monitoring had shown a day-time average diastolic BP of over 90 mmHg. Three doses of carvedilol (6.25, 12.5 and 25 mg daily) and placebo were then given double-blind in random order for periods of 4 weeks each. No period effects were detected. The antihypertensive effect was statistically significant at doses of 12.5 mg and 25 mg daily. There was, however, no evidence that 25 mg/day produced the peak effect. The lowest dose (6.25 mg/day) produced a small fall in both systolic and diastolic BP but neither of these were significant. We conclude that doses of 12.5 and 25 mg carvedilol once a day are adequate for the treatment of hypertension.