Analgesic effects of intrathecally administered celecoxib, a cyclooxygenase-2 inhibitor, in the tail flick test and the formalin test in rats.
BACKGROUND
The analgesic effects of celecoxib, a cyclooxygenase-2 (COX-2) inhibitor, on formalin-induced pain are still controversial. The purpose of this study was to examine the analgesic effects of intrathecally administered celecoxib on inflammatory induced pain, thermal-induced pain and hemodynamics.


METHODS
Male Sprague-Dawley rats with lumbar intrathecal catheters were tested via their tail withdrawal response to thermal stimulation (tail flick test) and via their paw flinching and shaking response to subcutaneous formalin injection into the hind paw (formalin test) after intrathecal administration of celecoxib. The blood pressure, pulse rate and behavioral side-effects were also examined.


RESULTS
Even the maximum available dose of celecoxib (200 microg/20 microl) had little effect in the tail flick test. In the formalin test, celecoxib induced a dose-dependent decrease in the flinch response in both phases 1 and 2. The 50% effective doses were 0.025 microg (95% confidence interval, 0.007-0.082 microg) in phase 1, 0.026 microg (0.010-0.045 microg) in phase 2a and 0.001 microg (0.00009-0.010 microg) in phase 2b. With the doses used in this study, the blood pressure and pulse rate did not change and no motor disturbance or behavioral side-effects were observed.


CONCLUSIONS
Intrathecal administration of celecoxib decreased inflammatory acute and facilitated pain without any hemodynamic or behavioral side-effects, but had no effect on acute thermal pain.
Nishiyama
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Department of Anesthesiology, Faculty of Medicine, University of Tokyo, Tokyo, Japan. nishit-tky@umin.ac.jp
D000698:Analgesia / Q000379:methods*; D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D000068579:Celecoxib; D052246:Cyclooxygenase 2 Inhibitors / Q000008:administration & dosage / Q000494:pharmacology*; D004202:Disinfectants / Q000008:administration & dosage / Q000009:adverse effects*; D004305:Dose-Response Relationship, Drug; D005557:Formaldehyde / Q000008:administration & dosage / Q000009:adverse effects*; D006439:Hemodynamics / Q000187:drug effects; D006358:Hot Temperature; D007249:Inflammation / Q000503:physiopathology; D007278:Injections, Spinal / Q000379:methods; D008297:Male; D009043:Motor Activity / Q000187:drug effects; D010146:Pain / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control*; D010812:Physical Stimulation / Q000379:methods; D011720:Pyrazoles / Q000008:administration & dosage / Q000494:pharmacology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D013449:Sulfonamides / Q000008:administration & dosage / Q000494:pharmacology*; D013997:Time Factors
D052246:Cyclooxygenase 2 Inhibitors; D004202:Disinfectants; D011720:Pyrazoles; D013449:Sulfonamides; D005557:Formaldehyde; D000068579:Celecoxib