Central nervous system actions of clonidine in hypertension.

Among 42 patients converted from clonidine to another antihypertensive medication, few sympathomimetic side effects were observed if the clonidine dosage had been less than 1.2 mg daily. Among a majority of 14 patients who had been taking larger doses, the previously reported syndrome of sympathetic hyperactivity was observed. It is particularly important to follow up patients who discontinue clonidine when this drug has been taken in excess of 1.2 mg daily.