Suppression of catecholamine excretion by low doses of clonidine in healthy subjects and feasibility study on clonidine application in angina pectoris.

The effect of low doses of clonidine (CL) (150 microgram/day p.o.) on catecholamine (CA) excretion, blood pressure (BP) and heart rate (HR) was investigated in a double-blind way on 9 healthy volunteers. CL administration for two consecutive days led to marked diminution of urinary CA, mainly of epinephrine, with only slight decrease in systolic BP and HR. The results show that this dose of CL is effective in suppressing adrenergic tone as reflected by the magnitude of CA excretion, without marked influence upon systemic BP. Subsequently, the same dose of the drug was administered for two weeks to 30 unselected patients with intractable angina known to be often associated with adrenergic overactivity. Clinical improvement manifested by complete disappearance of coronary pains or marked decrease in the incidence of anginal attacks was achieved in the majority (over 60%) of patients. Although best results were seen in patients with borderline hypertension, the drug was also effective in normotensive patients and no untoward hypotensive symptoms were noted throughout the trial. Blood CA and free fatty acids (FFA) measurements performed in 5 patients showed that favourable clinical effect of CL therapy coincides with lowering of CA and FFA levels. This study indicates that CL administered in a dose which does suppress adrenergic activity might be of value in the treatment of coronary patients. Favourable results of this preliminary trial incline to undertake well controlled clinical study.