We have studied the efficacy of clonidine hydrochloride administered transdermally once a week for 9 to 15 weeks in 12 patients with mild to moderate hypertension.
Clonidine reduced both supine and standing blood pressures on average, but only 8 subjects were responders, i.e. had a decrease in supine diastolic blood pressure to below 90 mm Hg or more than 10% from baseline. Supine heart rate was unchanged, but in the responders the orthostatic increase in heart rate was reduced by clonidine from baseline (p<0.05). moreover,="" in="" all="" the="" patients="" the="" change="" in="" the="" orthostatic="" increase="" in="" heart="" rate="" was="" correlated="" with="" the="" change="" in="" supine="" diastolic="" pressure="">p<>
Brachial artery blood flow, forearm arterial compliance, vascular resistance, and venous tone were not affected by clonidine.
Thus, transdermal clonidine reduced blood pressure, probably by a baroreflex-mediated effect, but did not affect the vasculature of the forearm.
Key words clonidine - hypertension - transdermal administration - baroreflex - arterial compliance