Attenuation of sleep propensity, core hypothermia, and peripheral heat loss after temazepam tolerance

1 Centre for Sleep Research, The University of South Australia, The Queen Elizabeth Hospital, Woodville, South Australia 5011; and 2 Department of Obstetrics and Gynaecology, The University of Adelaide, Adelaide, South Australia 5005, Australia If changes in thermoregulation mediate sleepiness induced by sedative/hypnotics, then a reduction in the soporific efficacy (tolerance) of these agents may be accompanied by a concomitant reduction in their thermoregulatory effects. We compared the thermoregulatory and soporific effects of acute temazepam (30 mg at 1400) in 11 young male subjects before and immediately after 7 consecutive days of temazepam (30 mg). Subjects lay supine (0800-2030), while foot (T ft ) and rectal (T c ) temperatures were recorded. Sleep onset latency (SOL) was measured hourly using 20-min multiple sleep latency tests. Relative to placebo, temazepam significantly reduced both T c and SOL ( 0.31°C and 14.1 min) while increasing T ft (3.39°C). A significant tolerance developed after the week of temazepam, with a mean reduction in soporific efficacy of 4.0 ± 0.8 min. This was accompanied by a concomitant attenuation in both T c ( 0.16°C) and T ft (1.44°C). Furthermore, SOL was temporally related to T ft and the maximum rate of decline in T c before and after tolerance. Together, these results indicate that the thermoregulatory system may be functionally involved in the regulation of sleepiness. heart rate; multiple sleep latency test; human male