Clonidine through the skin in the treatment of essential hypertension: is it practical?

The antihypertensive effects and side-effects of a clonidine transdermal therapeutic system (clonidine-TTS) were examined over 10 weeks in 22 patients with essential hypertension. The clonidine-TTS containing a 2.5 mg drug reservoir was designed to release 0.1 mg clonidine/24 h for seven days through a micropore rate-controlling membrane. In the total group mean systolic and diastolic blood pressure decreased from 162 +/- 14/106 +/- 4 mmHg to 137 +/- 17/92 +/- 8 mmHg after four weeks and 136 +/- 13/90 +/- 7 mmHg after 10 weeks (P less than 0.001). Five patients (23%) responded well to one clonidine-TTS (diastolic blood pressure less than or equal to 95 mmHg) and seven patients (32%) needed two clonidine-TTS. Additional oral therapy with 50 mg hydrochlorothiazide/day resulted in reduction of blood pressure to normal in six of the remaining 10 patients. This good pressure response was, however, accompanied by a high incidence of local allergic skin reactions of delayed type (type IV) in seven (32%) of the 22 cases. Patch testing with various components of clonidine-TTS which was performed in four of the seven patients showed in three cases allergic contact dermatitis to clonidine. Our results demonstrate a good and sustained antihypertensive action of clonidine-TTS. However, the extraordinarily high incidence of skin allergy to clonidine limits its use in the treatment of essential hypertension.