Clinical experience with rate-controlled delivery of antihypertensive therapy by a transdermal system.

The efficacy of transdermal clonidine, alone and in combination with diuretics, has been demonstrated in several studies involving patients with mild to moderate essential hypertension. In one 3-month open study, 64% of patients (wearing one to three 3.5 cm2 transdermal patches) achieved sustained blood pressure reductions throughout the treatment period. In this large study, side effects requiring discontinuation of drug were not observed. Transdermal clonidine reduced plasma renin activity and urinary aldosterone excretion to the same extent as that reported for oral clonidine. Renal function or serum electrolytes were not affected during therapy with transdermal clonidine. Another study showed that patients receiving oral clonidine and hydrochlorothiazide experienced comparable blood pressure reductions when switched to transdermal patches. Plasma drug concentrations measured during treatment with the transdermal patches were similar to the trough levels observed during treatment with oral clonidine. The equipotency of oral and transdermal therapy in combination with hydrochlorothiazide was also demonstrated in two remaining studies. In one of these studies it was suggested that daily variations in blood pressure induced by the peak and trough drug levels of the oral form were minimized by the stable drug levels characteristics of the transdermal device.