Differences in psychic performance with guanfacine and clonidine in normotensive subjects.

Abstract

1 Doses of clonidine 0.15 mg or guanfacine 1.0 mg, respectively, and 2 h later additional doses of clonidine 0.3 mg or guanfacine 2.0 mg, respectively, were given to 24 healthy students. 2 Blood pressure was reduced by the same amount by both drugs. 3 Plasma noradrenaline concentrations decreased with both drugs, but the reduction was significantly greater following the administration of clonidine. 4 Mental activity in the EEG was less suppressed in the guanfacine group than in the clonidine group. The differences were statistically significant. 5 Self-estimations for well-being and mood showed only small changes due to guanfacine but significant changes due to clonidine. 6 The decrease of information processing and the increase in reaction time, measured by performance in different psychometric tests, were significantly more pronounced after clonidine treatment than guanfacine. 7 A dose-response relationship could only be observed in vigilosomnograms, in the tests of selfestimation related to well-being and mood and in the decrease in plasma noradrenaline in the clonidine group. 8 It was concluded that guanfacine had a lesser CNS depressant action than clonidine, when administered in equipotent hypotensive doses.

Electroencephalographic and Psychometric Assessment of the CNS Effects of Single Doses of Guanfacine Hydrochloride (Estulic®) and Clonidine (Catapres®)

“…In human volunteers, a study of the relative effects of clonidine and guanfacine on noradrenaline concentra tion, EEG parameters and psychometric test performance showed significant differences between these drugs, clon idine having a stronger effect [ 17], A possible explanation for the different effects between guanfacine and clonidine might involve the existence of different types of a-adren ergic receptors [14],…”

Clonidine disrupts aged‐monkey delayed response performance

“…In any case, clonidine impairs cognitive performance of young human volunteers [Speigel and Devos, 1980;Kugler et al, 1980;Falkner et al, 19841. The effects of clonidine on the cognitive performance of normal aged and SDAT patients have not been reported.…”

Effects of clonidine and guanfacine in essential hypertension

“…15, 3z3 49 Our data also support reports that the antihypertensive effect of clonidine in patients in the supine position is the consequence of the decrease in C0,143 373 38 while that of guanfacine is mainly the result of the decrease in TPR.31, 453 47 Different adrenoceptorsZ5 as well as different sites of action within the CNS50 have already been suggested as explanations. Differences in hemodynamic or central actions and in side effects between clonidine and guanfacines, 26,49 may reflect, at least in part, different modes of action. The decrease in plasma concentrations of norepinephrine was greater with clonidine than with guanfacine, and the decrease in information processing or the increase in reaction time were much greater after clonidine than after guanfacine applied in equipotent hypotensive doses.z6 Clonidine was followed by a substantial and dose-dependent reduction in rapid eye movement (REM) sleep, while guanfacine did not alter REM sleep.5z The tricyclic antidepressant desmethylimipramine markedly reduced the antihypertensive effect of ~l o n i d i n e ,~ whereas in combination with guanfacine it elicited an additional decrease in blood pressure.21 Activation of CNS histamine Hz-receptors seems to contribute to the hypotensive action of clonidine in ratsz2 but not in normotensive man57 and not to the effect of g~a n f a c i n e .~~ Topical application of clonidine to the ventral surface of the medulla oblongata in the cat induced a marked fall in blood pressure and heart rate, whereas guanfacine was not effective in this test model and, unlike clonidine, did not reduce CNS dopamine turnover.…”