Comparison of effect on psychomotor performance of single doses of propranolol and acebutolol

Propranolol has recently been shown to produce some impairment of psychomotor performance in human volunteers. This beta-blocking compound, however, is lipophilic and readily penetrates the blood-brain barrier to gain access to the central nervous system. Acebutolol has a lower lipid solubility. A study was carried out, therefore, to compare the psychomotor effect of the two beta-blocking drugs. Any subjectively experienced side-effects were also recorded. Ten healthy volunteers were given single doses of 40 mg propranolol, 100 mg acebutolol and placebo on a random double-blind basis and the effect, if any, on performance was measured using a particularly sensitive complex reaction time technique. Propranolol produced a significant prolongation of complex reaction time when compared with placebo or acebutolol. Acebutolol did not significantly increase complex reaction time over the placebo value. Two subjects reported mild feelings of 'muzziness' after taking propranolol. No side-effects were reported after acebutolol.