Antithrombotic therapy with oral aspirin (ASA) or clopidogrel (CLO) (Plavix®; Bristol-Myers Squibb, Bridgewater, NJ) is associated with an attenuated skin vasodilator response and a greater rate of rise in core temperature in healthy, middle-age individuals during passive heating in a water perfused suit.
Purpose: The present double-blind, crossover study examined the functional consequences of 7 d of low-dose ASA (81 mg·d−1) versus CLO (75 mg·d−1) treatment in 14 healthy, middle-age (50–65 yr) men and women during passive heating in air (40 min at 30°C, 40% relative humidity) followed by exercise (60% V˙O2peak).
Methods: Oral temperature (Tor) was measured in the antechamber (23.0°C ± 0.1°C) before entering a warm environmental chamber. After 40 min of rest, subjects cycled on a recumbent cycle ergometer for up to 120 min. Esophageal temperature (Tes) and laser Doppler flux were measured continuously, and the latter was normalized to maximal cutaneous vascular conductance (%CVCmax).
Results: Before entry into the environmental chamber there were no differences in Tor among treatments; however, after 40 min of rest in the heat, Tes was significantly higher for ASA and CLO versus placebo (37.2°C ± 0.1°C, 37.3°C ± 0.1°C, vs 37.0°C ± 0.1°C, both P < 0.001), a difference that persisted throughout exercise (P < 0.001 vs placebo). The mean body temperature thresholds for the onset of cutaneous vasodilation were shifted to the right for both ASA and CLO during exercise (P < 0.05).
Conclusion: ASA and CLO resulted in elevated core temperatures during passive heat stress and shifted the onset of peripheral thermoeffector mechanisms toward higher body temperatures during exercise heat stress.
Noll Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, PA
Address for correspondence: Lacy M. Alexander, Ph.D., The Pennsylvania State University, 113 Noll Laboratory, University Park, PA 16802; E-mail: firstname.lastname@example.org.
Submitted for publication July 2012.
Accepted for publication October 2012.