Analgesic Actions After Local Peripheral Administration Of Lornoxicam In A Model Of Formalin Test In The Rat

OBJECTIVE and BACKGROUND: The formalin test in rat is avalid and reliable model of nociception and the subcutaneous injection of formalin produced a biphasic Pain response in rats. The second phase mediated by prostaglandins. prostaglandin play an important role in inflammation reaction. The non-steroidalanti-inflammatorydrug (NSAIDS) Xafon(Lornoxicam), an oxicam derivative as a cyclo- oxygenase (COX) inhibitor, is equipotent in the inhibition of both COX1 and COX2 in a series of vitro studies, is thought to attenuate the inflammatory prosess and play analgesic activity in related to the inhibitory action on prostaglandin synthesis ,via inhibition of COX activity in the COX pathway of arachidonic acid metabolism ,but not cause inhibition of 5-Lipoxygenase.In a series of studies Lornoxicam is administered intraperitoneally, intravenously, intramuscularsly. In this study ,we examined analgesic actions after local peripheral administration of Lornoxicam in a rat model of formalintest. In order to provide the evidence for clinical use.MATERIAL and METHOD: Fifty-six male Spague-Dawley rats wererandomly divided into 3 groups of 8 animals each:Control group ;30 minutes prior to receiving subcutaneous injections of 5% formalin 5Ojul into the plantar surface of the right hind-paw,groupA received Lornoxicam (0.7mg/Kg ,1 mg/Kg,1.429 mg/Kg) in ipsilateral plantar surface of the hindpaw, group B received Lornoxicam (0.7mg/Kg ,1 mg/Kg, 1.429 mg/Kg) in contralateral plantar surface of the hindpaw. Pain response was record for a period of 60 minutes .The sumnation of time(in seconds)spent in licking and biting responses of the injected paw during each 5 minutes block.RESULT:1. The pain response in the first phase (frome 0-10 minutes)wasn't inhibited in group B and A. (P>0.05) .2. The pain response in the second phase (frome 10-60 minutes)was inhibited in groupA( 1 mg/Kg,1.429 mg/Kg P<0.01; 0.7mg/Kg P <0.05) ,but not inhibited in group B . The time of licking and biting is shoitage in group A than in group B.3. The second phase inhibition rate in group Q is reducing compare to group P\.CONCLUSION:1. Lornoxicam has no effect in the first phase in formalin test in rats.2. For the second phase:local peripheral administration of Lornoxicam (0.7mg/Kg^ 1 mg/Kg > 1.429 mg/Kg ) reduce the biting/ licking timewhen Formalin was injected into the same site in a model of formalin test. It suggest they have analgesic effect.3. The analgesic effect has trend of positive relevance with dosage.4. When rats Received Lornoxicam in unilateral plantar surface of the hindpaw, Formalin was injected in 50 ul into contralateral plantar surface of the hindpaw(group B). The biting/ licking time of contralateral hindpaw didn't reduced, suggest that local peripheral administration of Lornoxicam has no analgesic effect on contralateral hindpaw.5. From above , local peripheral administration of Lornoxicam has analgesic effect witch producted through local but not systemic mechanism.