REDUCTION OF POSTBURN HYPERALGESIA AFTER LOCAL INJECTION OF KETOROLACIN HEALTHY-VOLUNTEERS

Background: Nonsteroidal antiiflammatory drugs may be particularly eff ective against prostaglandin-mediated, postinjury hyperalgesia and rel ated inflammatory pain. However, their usefulness may be limited by th eir systemic side effects. The current study determined if local effec tiveness can be achieved by low-dose intradermal nonsteroidal antiifla mmatory drug administration. Methods: Ten healthy volunteers were aske d to make magnitude estimations of the pain induced by a contact therm al stimulator at 1 degrees C increments between 43 and 51 degrees C at three 1 X 1 cm study sites on each forearm during three study phases: (1) baseline; (2) after pretreatment with 10 mu l 0.9% saline (n = 1 site on each forearm), 0.3 mg ketorolac (n = 1 on each forearm), or no thing (n = 1 on each forearm); and (3) after ''injury'' by a mild burn at the ketorolac- and saline-treated sites on one arm or by injection of 10 nmol bradykinin at all three sites on the other arm. The effect s of pretreatment on the pain induced by thermal testing were assessed using repeated-measures analysis of variance. Results Pretreatment wi th ketorolac had a selective effect on the postburn injury hyperalgesi a, reducing the increase In pain intensity (P < 0.05) but not the decl ine in pain threshold. It had no effect on the responses to thermal st imuli before injury or on the pain of burning, which were similar at k etorolac- and saline-treated sites. The effect of pretreatment with ke torolac on bradykinin-induced hyperalgesia could not be tested because hyperalgesia was not achieved after bradykinin infection at sites pre treated with saline as well as ketorolac. Conclusions: The findings in dicated that local infection of ketorolac can provide local analgesia. The selective nature of the ketorolac-induced analgesia may account f or the partial effectiveness of nonsteroidal antiinflammatory drugs in clinical settings.