Effect of modafinil on heat production and regulation of body temperatures in cold-exposed humans.
Military personnel often undergo sustained operations that affect vigilance and alertness. Pharmacological agents may be used to enhance vigilance. Most such agents also have thermogenic properties. Whether a new promising stimulant, modafinil (Lyons and French, Aviat. Space Environ. Med. 1991; 62:432-435), has a beneficial effect on cold tolerance in the military context, is not known. The goal of this study was, therefore, to evaluate the effect of this new drug on thermal balance and the regulation of body temperatures in neutral conditions and when challenged by a cold exposure. Nine subjects underwent three trials each: two in the cold (3 h at rest, 10 degrees C) 0.5 h after the ingestion of either placebo or modafinil (200 mg), and one in thermal neutrality with modafinil (same conditions except Tdb = 29.3 degrees C). As expected, cold produced a drop in Tre and Tsk and an increase in Vo2. Although non-significant, there was a tendency for a slightly greater drop in Tre with modafinil (0.65 degrees C vs. 0.57 degrees C with placebo). A similar tendency was found for the heat debt (S) which was greater with modafinil than with placebo (16.1 +/- 0.7 vs. 14.7 +/- 0.6 kJ.kg-1, respectively, +9.5%, p = 0.11). This tendency appears to be the combined result of a slightly lower mean heat production during the test and a slightly greater mean dry heat loss. When tested at thermal neutrality, the drug had no effect on any thermal or metabolic parameters. The results demonstrate that the ingestion of a single dose of modafinil has no significant acute effect on thermal balance in neutral conditions and on thermoregulation in normal subjects exposed to cold. However, a tendency for slightly greater cooling was noted with modafinil. It is not known whether the use of modafinil in conjunction with sleep deprivation (a likely scenario) could magnify this effect.
Defence & Civil Institute of Environmental Medicine, North York, Ontario, Canada.
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Bourdon
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Jacobs
W A
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Bateman
A L
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Vallerand
D000328:Adult; D001559:Benzhydryl Compounds / Q000494:pharmacology*; D001831:Body Temperature / Q000187:drug effects; D001833:Body Temperature Regulation / Q000187:drug effects*; D000697:Central Nervous System Stimulants / Q000494:pharmacology*; D003080:Cold Temperature; D006801:Humans; D008297:Male; D008889:Military Personnel; D000077408:Modafinil; D010101:Oxygen Consumption / Q000187:drug effects
D001559:Benzhydryl Compounds; D000697:Central Nervous System Stimulants; D000077408:Modafinil