Analgesic effects of dexamethasone in burn injury.

BACKGROUND AND OBJECTIVES

Glucocorticoids are well-known adjuvant analgesics in certain chronic pain states. There is, however, a paucity of data on their analgesic efficacy in acute pain. Therefore, the aim of the study was to examine the analgesic effects of dexamethasone in a validated burn model of acute inflammatory pain in humans.

METHODS

Twenty-two volunteers were investigated in a double-blind, randomized, placebo-controlled cross-over study. Intravenous dexamethasone 8 mg or placebo was administered on 2 separate study days. Two hours after drug administration, a first-degree burn injury was produced on the medial aspect of the nondominant calf (12.5 cm2, 47 degrees C for 7 minutes). Quantitative sensory testing included pain ratings to thermal and mechanical stimuli (visual analog scale [VAS]), assessments of thermal and mechanical detection thresholds, and areas of allodynia and secondary hyperalgesia.

RESULTS

The burn injury induced significant increases in erythema (P <.0001) and hyperalgesia (P <.001) in both groups. Pain ratings and development of tactile allodynia during the burn did not differ between dexamethasone and placebo treatments (P >.6). There were no significant differences between treatments in regard to skin erythema (P >.8), thermal or mechanical thresholds (P >.2), thermal or mechanical pain response (P >.2), or mechanical secondary hyperalgesia (P >.2). Dexamethasone had no analgesic effects in normal skin.

CONCLUSIONS

The study indicates that systemic administration of dexamethasone 2 hours before a burn injury does not reduce the inflammatory-mediated changes in quantitative sensory thresholds, pain perception, or skin erythema in humans.