Suriclone enhances the actions of chlorpromazine on human psychomotor performance but not on memory or plasma prolactin in healthy subjects

Abstract

Twelve healthy subjects received single oral doses of 0.4 mg suriclone (SU), 7.5 mg zopiclone (ZO) and placebo, alone and together with 50 mg chlorpromazine (CP), double blind and crossover, in Latin square order, at one-week intervals. Performance tests administered before and 1.5, 3.5 and 6 h after drug intake included digit symbol substitution and simulated driving combined in a "Global test", flicker fusion frequency, body balance and memory and subjective assessments. Changes from baseline were examined statistically. Performance and memory data were analysed from only 11 subjects. Compared to placebo, SU minimally affected "global" performance, although it slowed reactions and tended to impair digit substitution. ZO impaired "global" performance at 1.5 h, affected performance in several separate tests, and produced subjective muzziness. CP did not impair "global" performance, although it did impair digit substitution and render the subjects drowsy, weak and dreamy. The combinations SU + CP and ZO + CP definitely impaired "global" performance more than CP alone. This difference was also found in most objective tests but less so in the subjective tests. CP and its combinations produced similar increases in plasma prolactin. Active drugs and their combinations variably lowered blood pressure and increased heart rate, and one subject collapsed after CP. The treatments irregularly impaired spatial memory and learning acquisition. No pharmacokinetic interactions were seen in the plasma levels of suriclone, zopiclone and chlorpromazine. The impairment of performance after these combinations resembles that previously encountered after 2.5 mg lorazepam, or 15 mg diazepam + 100 mg remoxipride.