The effect of opioids on thermoregulatory responses in humans and the special antishivering action of meperidine.

In summary, both mu-receptor and combined mu/kappa-receptor opioids impair thermoregulatory control. Alfentanil, a pure mu-receptor agonist slightly increased the thresholds for sweating and markedly decreased the thresholds for vasoconstriction and shivering. However, the vasoconstriction-to-shivering range remained normal during alfentanil administration as it does during general anesthesia. Meperidine, a combined mu- and kappa-receptor agonist, also slightly increased the threshold for sweating and reduced the thresholds for vasoconstriction. However, meperidine reduced the shivering threshold twice as much as the vasoconstriction threshold, thus significantly increasing the vasoconstriction-to-shivering range. Furthermore, shivering during meperidine administration, once triggered, was of low intensity suggesting that the drug also decreased the gain of shivering. The special antishivering action of meperidine appears to result, at least in part, from its kappa-receptor activity.