Psychophysiological effects and dose equivalence of zopiclone and triazolam administered to healthy volunteers. Methodological considerations.

1. Dose-equivalence studies of zopiclone and triazolam were carried out. 2. Zopiclone (6.25, 8.75 and 11.25 mg), triazolam (0.1875, 0.375 and 0.5 mg) and placebo were given in the morning to 14 healthy male volunteers aged 20-25 years under double-blind conditions according to an incomplete block design. Each patient received three of the seven possible treatments at intervals of at least 1 week. Subjects were evaluated using physiological measures, rating scales and memory tasks before and 1.5 and 4.5 h after drug administration. 3. The sedative and amnestic effects of zopiclone were qualitatively similar to those of triazolam, with the highest dose of each having the greatest effect. 4. On the basis of the digit symbol substitution test, 10 mg of zopiclone is equivalent to 0.5 mg of triazolam. Methodological problems of the experimental design of dose-equivalence studies are discussed.