Guanfacine ( tenex), an a2 agonist, is more selective for a2 receptors than is clonidine. Guanfacine lowers blood pressure by activation of brainstem receptors with resultant suppression of sympathetic activity. The drug is well absorbed after oral administration. About 50% of guanfacine appears unchanged in the urine; the rest is metabolized. The t122 for elimination ranges from 12—24 hours. Guanfacine and clonidine appear to have similar efficacy for the treatment of hypertension and a similar pattern of adverse effects. A withdrawal syndrome may occur after abrupt discontinuation, but it is less frequent and milder than the syndrome that follows clonidine withdrawal, perhaps reflecting the longer t122 of guanfacine.
Was this article helpful?