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

If changes in thermoregulation mediate sleepiness induced by sedative/hypno tics, then a reduction in the soporific efficacy (tolerance) of these agent s may be accompanied by a concomitant reduction in their thermoregulatory e ffects. We compared the thermoregulatory and soporific effects of acute tem azepam (30 mg at 1400) in 11 young male subjects before and immediately aft er 7 consecutive days of temazepam (30 mg). Subjects lay supine (0800-2030) , while foot (T-ft) and rectal (T-c) temperatures were recorded. Sleep onse t latency (SOL) was measured hourly using 20-min multiple sleep latency tes ts. 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 sig nificant tolerance developed after the week of temazepam, with a mean reduc tion in soporific efficacy of 4.0 +/- 0.8 min. This was accompanied by a co ncomitant 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 d ecline in T-c before and after tolerance. Together, these results indicate that the thermoregulatory system may be functionally involved in the regula tion of sleepiness.