This study. one of the serial studies, is concerned with effects of hypontics on cognitive function, given in a typical therapeutic dosage at bedtime.
Triazolam 0.25mg zopiclone 0.75mg or placebo were administrated orally to normal male adult subjects at bedtime. This study took place in three consecutive seesions separated by one week interval in accordance with a repeated measures
double-blind
design with the order of the drugs counterbalanced over the subjects.
Cognitive performance was assessed at 30 minutes. Four hours and eight hours after the administration of the drugs using a battery of cognitive tests(continuous arithmetic, digit span. Symbol copy, digit symbol substitution test, and free
recall).
In all the tests except digit span, the performance was significantly affected by the time of assessment but not by the drug condition. The performance generally decreased 4 hours after treatment and then improved 8 after treatment approximately
to
the
performance level at the 30 minutes after treatment, Specifically this effect of the testing times was more sensitive in both zopiclone and triazolam conditions than in the placebo condition.
In free recall test a significant interaction between drug condition and testing time was also found. Follow-up analysis of this interaction showed that zopiclone condition significantly impaired performance compared to both triazolam and the
placebo
condition, at four hours after treatment however there was no difference amongest the drug conditions at 30 minutes and eight after treatment.
These results suggest that extent to which the cognitive performance is impaired by single therapeutic doses of triazolam and zopiclone administered at bedtime seems to be ascribed to the testing times rather than the hypnotics. But this
interpretation
should be considered in terms of circadian rhythms of sleepiness and cognition, sleepiness secondary to the hypnotics. pharmacokinetics and sensitivity of the cognitive cognitive tests.
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