[Effect of preemptive intrathecal lornoxicam on foot swelling of formalin test in rats].

Objective: To investigate the anti-inflammatory effect of preemptive intrathecal Lornoxicam on foot swelling of formalin test in rats.

Methods: Eighteen healthy male adult Sprague-Dawley (SD) rats (about 250 g) were randomized into 3 groups: intrathecal solvent group (group S, solvent 20 microL), intramuscular Lornoxicam group (group IM, Lornoxicam 300 microg/20 microL) and intrathecal Lornoxicam group (group IT, Lornoxicam 300 microg/20 microL). After measuring the basic volumes of the left hind paws, rats were injected with corresponding solution intrathecally or intramuscularly, and followed by an intra-plantar administration of 100 microL of 5% formalin 10 minutes later. The volumes of left hind paws were measured again at 10 min, 30 min, 1 h, 2 h, 3 h, 4 h, 24 h after formalin injection.

Results: There was no statistical difference of weights or basic volumes among three groups. At 10 min after formalin injection, the left hind paw volume of group IT [(1.53 +/- 0.06) mL] were smaller than that of group S [(1.67 +/- 0.09) mL], P=0.039, but there was no statistically difference between group IT and group IM [(1.65 +/- 0.06) mL]. At 30 min after formalin injection, the left hind paw volume of group S [(1.88 +/- 0.88) mL] was larger than that of group IM [(1.77 +/- 0.05) mL, P<0.05] and group IT [(1.61 +/- 0.06) mL, P<0.01]. The feet swelling degree of group IT was less than that of group IM, P<0.05. At 1 h, 2 h and 3 h after formalin injection, the left hind paw volume of group S was similar to that of group IM, and the volume of group IT was smaller than the other two groups. At 4 h and 24 h after formalin injection, there were no statistic differences of the left hind paw volume among the three groups.

Conclusion: At 10 min to 3 h after formalin injection, swelling of rat feet induced by formalin was alleviated by preemptive intrathecal Lornoxicam.