Cicletanine chlorhydrate (C), a furopyridine derivative, is a new antihypertensive drug that acts mainly by enhancing endogenous prostacyclin release. It has been shown to induce a significant, progressive reduction in systolic and diastolic blood pressure in patients over 60 years of age at a daily dose of 150 mg in a placebo-controlled efficacy trial. As concurrent studies in adult hypertensive patients demonstrated an antihypertensive effect at even lower doses, we further compared the antihypertensive efficacy and tolerance of 50 mg vs 100 mg daily dose of C in elderly hypertensive patients in order to determine the lowest active posology. A prospective, double-blind randomized trial included 72 patients (56 female, 16 male) aged 65 years or more (mean age +/- 1 SD: 80.3 +/- 5.9 years, range 65-90) with moderate, essential hypertension, and normal-for-age renal function whose diastolic BP was greater than 95 mmHg and/or systolic BP was greater than 160 mmHg after 15 days of a single-blind placebo period. They were randomly allocated to either 50 mg (group I, 36 patients) or 100 mg (group II, 36 patients) C given in a single morning dose for 3 months with monthly surveillance. Of them, 60 achieved satisfactory BP control with C as monotherapy and completed full follow-up.(ABSTRACT TRUNCATED AT 250 WORDS)