Effects of acute and repeated doses of two muscle relaxants chlormezanone and thiocolchicoside, on vigilance and psychomotor performance of healthy volunteers

This was a randomized double blind, placebo‐controlled cross over study performed on 12 healthy female volunteers. It consisted of three treatment sessions of 7 days separated by a one week wash out period. The objectives of the study were to assess the sedative activity of 2 muscle relaxant drugs: chlormezanone (600 mg daily) and thiocolchicoside (16 mg daily) after a single oral administration and at steady state (day 7). The drugs were administered orally, during each treatment period as 3 capsules daily for 7 days. Assessment criteria explored psychometric tests, body sway and subjective feeling rating scales. Chlormezanone induced objective disturbances of vigilance and concentration characterised by a decrease in the performance of an arithmetic calculation test and an increase in body sway area recorded in comparison with thiocolchicoside and placebo. These impairments were mainly marked on steady state. Most of the volunteers (10 over 12) complained of drowsiness throughout this treatment. Thiocolchicoside was devoided of any objective or subjective sedative side effect.