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

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 degrees C and 14.1 min) while increasing T-ft (3.39 degrees 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 degrees C) and Tft (1.44 degrees C). Furthermore, SOL was temporally related to Tft 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.