Today's Veterinary Practice

MAY-JUN 2014

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25 aCUTe PaIN IN CaTS: TreaTmeNT wITh NSaIDS | May/June 2014 Today's Veterinary Practice tvpjournal.com NSAIDs are one of the most common drug classes used to treat pain, and there is a robust body of infor- mation indicating that NSAIDs are effective in treating acute pain in cats. 6,7 They have antipyretic, analgesic, and anti-inflammatory properties, which make them appealing therapeutic options; however, remember that there is not, and never will be, a completely safe NSAID for use in cats. IS THERE AN IDEAL NSAID FOR USE IN CATS? Based on our current understanding and the informa- tion available, if we were to design an ideal NSAID for use in cats, it would have certain important character- istics (Table 1). 1. Spares COX-1 & Targets COX-2 NSAIDs work by inhibiting the production of prosta- glandins (see The Role of Prostaglandins) from ara- chidonic acid by the enzyme cyclooxygenase (COX). There are 2 forms of the COX enzyme: Figure 1. The role of prostaglandins in the periphery as sensitiz- ers of pain fibers is well known. They are also involved in the facili- tation and amplification of pain signals at various levels in the cen- tral nervous system; for example, central sensitization is assisted by prostanoids found in the dorsal horn of the spinal cord. Additionally, recent information suggests that locally produced prostanoids help decrease brain function in the areas involved in descending control over pain (endogenous analgesic systems). Altered descending control over pain Altered processing at the level of the spinal cord Altered transduction in the periphery THE ROLE OF PROSTAgLANDINS Prostaglandins are required for both everyday and compensatory functions of all organs and tissues. For example, prostaglandins are involved in GI protection and healing of GI ulcers as well as nor- mal renal function and compensatory protective mechanisms of the kidney during hypovolemia. 10 Prostaglandins are a predominant player in the production of pain in the periphery through sensitization of nerves. They are also involved in the processes of facilitation and amplification of noxious stimuli during central sensitization at the level of the dorsal horn of the spinal cord (Figure 1). 12 Central sensitization has been shown, in vet- erinary species, to become established within 24 hours of a surgical procedure, and it contributes to postoperative pain and likely chronic pain. • COX-1: Generally constitutive and involved in production of prosta- glandins that protect gastric muco- sa and maintain normal platelet function and renal perfusion • COX-2: Generally induced during inflammation and plays a role in healing and pain signaling; 8 how- ever, its activity also produces prostanoids involved in the nor- mal function of certain tissues, such as the kidneys, brain, and reproductive system. The ideal NSAID strikes a balance between COX-1 and COX-2 inhibi- tion: • Nonselective COX inhibitors equally inhibit COX-1 and COX- 2. 9 These NSAIDs tend to be asso- ciated with classic NSAID side effects, such as gastrointestinal (GI) ulceration, anorexia, vomit- ing, diarrhea, and renal and liver toxicity. 10 • COX inhibitors that selective- ly inhibited COX-2 demon- strated a greater safety margin than nonselective COX inhibi- tors in initial studies in healthy humans. However, this great- er safety margin does not hold true for humans at risk for GI side effects. 11 Nothing is known about the relative risk of selec- tive COX-2 inhibitors in veteri- nary medicine. TVP_2014-0506_FelinePainMgmt (Part 2).indd 25 5/23/2014 11:23:08 AM

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