Effect of clonidine and yohimbine on sleep in healthy men: a double-blind, randomized, controlled trial.
OBJECTIVE: To study the acute effect of clonidine, an alpha 2-adrenoceptor agonist, and yohimbine, an alpha 2-adrenoceptor antagonist, on nocturnal sleep in healthy men. SETTING: McGuire Veteran Affairs Medical Center, Richmond, Virginia, USA. SUBJECTS: Eight healthy male volunteers. METHODS: Each subject slept in the sleep laboratory for 2 consecutive nights on three separate sessions, at 3-week intervals. On the 2nd night of each session, the subjects received yohimbine (5.4 mg), clonidine (0.1 mg), or placebo in a double-blind, randomized, placebo-controlled, crossover design. RESULTS: There were no apparent effects of yohimbine. In contrast, clonidine completely suppressed rapid eye movement (REM) sleep in one subject and reduced REM sleep in the remaining seven subjects. CONCLUSION: Our study confirms that clonidine markedly decreases REM, even at a low single dose, and supports the hypothesis of the important role of alpha 2-receptors in controlling REM sleep.