EFFECT OF TRIAZOLAM ON RESPONSES TO A COLD-WATER IMMERSION IN HUMANS

Managing alertness of soldiers during sustained operations is a source of serious concern for military unit commanders. A frequently employe d strategy is to induce sleep before an operation, especially operatio ns requiring prolonged travel. Sleep-inducing drugs could have an acti on on thermoregulation through their effect on alertness and a possibl e direct effect on the brain. The goal of this study was therefore to evaluate the effect of a commonly prescribed triazolam (Halcion (R)) o n thermoregulatory responses to cold-water immersion. Eight subjects w ere immersed twice in 18 degrees C water for up to 90 min in the morni ng; once after ingesting 0.25 mg triazolam (TRZ) the prior evening, an d again after placebo (PLB) treatment. There were no significant diffe rences between trials for mean duration of the immersion, the change i n rectal temperature and mean skin temperature. Total metabolic heat p roduction was similar for both conditions: 767 +/- 107 vs. 781 +/- 105 kj . m(-2) for TRZ and PLB, respectively. The results should be consi dered in light of a large variation among the subjects in sensitivity to TRZ, which was unrelated to biometrical characteristics such as sur face area-to-mass ratio, lean body mass, % body fat, and physical fitn ess. Although not statistically significant, there was a trend for a s matter increase in plasma free fatty acid and glycerol concentrations after water immersion with TRZ. The results suggest that the ingestion of a single dose of triazolam 11 h prior to a cold-water immersion is not likely to accelerate the rate of onset of hypothermia. Individual sensitivity, however, may predispose some sensitive subjects to negat ive effects in this regard.