The effects of 20-mg doses of the short-acting benzodiazepine, temazepam, on sleep, performance and pineal, adrenal and temperature rhythms were investigated in a placebo-controlled, double-blind crossover study. Ten healthy males were studied 4 d prior to flying from Sydney to London via Tokyo and Anchorage (11 time zones). Temazepam or placebo were administered at 2300 hours (local time) during the flight and for 4 d after arrival. After a 7-d recreation break in London, the subjects returned to Sydney via Moscow and Tokyo and again took five doses of temazepam or placebo. During the 5 d following their arrival in London or Sydney, the subjects collected urine, had rectal temperature monitored, performed a battery of performance tests and filled out questionnaires. Temazepam significantly improved various subjective sleep characteristics, particularly on the first few nights. Performance (choice reaction time, critical flicker fusion threshold and pencil and paper tests) was not impaired by temazepam treatment. The pineal rhythm was assessed by urinary 6-sulphatoxymelatonin excretion rate determinations. The time of peak 6-sulphatoxymelatonin excretion (acrophase) occurred progressively later each day after arrival in London and Sydney, however the rate of adjustment of the rhythm was not affected by temazepam. Similarly, the urinary cortisol and temperature rhythms adjusted to the new environments by progressive delay with no drug effect being evident. Administration of temazepam clearly had a beneficial effect on sleep and alertness following transmeridian travel, without detrimental effects on performance. There was no evidence to suggest that temazepam altered the rates of entrainment of physiological rhythms to the new environments.
