Electroencephalographic and psychometric assessment of the CNS effects of single doses of guanfacine hydrochloride (Estulic) and clonidine (Catapres).

A double-blind, placebo-controlled study was carried out in 10 young healthy volunteers to investigate the effects of single doses of 1 and 2 mg guanfacine hydrochloride (Estulic) and 0.15 and 0.3 mg clonidine (Catapres) on the electroencephalogram (EEG), subjective mental and emotional state, blood pressure and heart rate. These doses are considered to be equipotent with regard to their antihypertensive effects, as shown in long-term therapeutic trials. Each subject received all five treatments in random sequence at intervals of 1 week. The EEG tracings were evaluated quantitatively by spectral analysis. Procedures were carried out before and at 1, 2, 4, 6 and 8 h after drug administration. After clonidine the EEG showed increased slow-wave activity and decreased alpha activity, these effects being dose-dependent. They were of the sedative type and did not clearly indicate specific psychotropic properties. The subjective mental and emotional state questionnaire indicated a decrease of alertness, extroversion, concentration and mood (in that order), changes which paralleled the EEG changes. The changes observed after guanfacine were qualitatively similar to those after clonidine, but were of considerably lower intensity. Our data suggest that guanfacine has less central nervous system-depressant activity than clonidine.