INTRATHECAL KETOROLAC TROMETHAMINE PRODUCES ANALGESIA AFTER CHRONIC CONSTRICTION INJURY OF SCIATIC-NERVE IN RAT

Purpose: The study compared analgesic efficacy of intrathecally admini stered ketorolac tromethamine (K) and morphine hydrochloride (M) (in e quimolar doses) in the chronic neuropathic pain model, induced by chro nic constriction injury (CCI) of the sciatic nerve in rat. Methods: Ma le Sprague-Dawley rats (n = 30) were anaesthetized with halothane and an intrathecal catheter was inserted to the mid-lumbar level of the sp inal cord. On the 5th postoperative day, rats were anaesthetized with halothane and four ligatures were loosely applied around the right sci atic nerve. Seven days later, those animals were randomly divided into three groups and were injected with either saline, M (20 nmoles) or K (20 nmoles). Two pain responses (foot-withdrawal delay and hind paw e levation time) were measured on both sides using the radiant heat meth od. Further thermal (''cold'') allodynia was assessed by measuring of the total time of hindpaw elevation in animals placed on the cold meta l plate. Results: Twenty nmoles of M and K injected intrathecally prod uced decrease of differential pain score calculated for both measured responses (hind paw withdrawal and hind paw elevation), compared with saline injected animals (P < 0.05). The reduction in pain response pro duced by K was less (P < 0.05) than the reduction in pain response obs erved in the animals receiving intrathecal M. Measurement of cold allo dynia revealed that the animals in M and K injected groups demonstrate d decreases in the total hind paw elevation time, when compared with s aline-injected animals (P < 0.05). Conclusion: M and K produced hypoal gesia after intrathecal administration in rats with CCI, with M being more potent than K at an equimolar dose range. The analgesic effect of K was equal to equimolar doses of M for alleviation of cold allodynia .