Repeated administration of low dose ketamine for the treatment of monoarthritic pain in the rat

The aim of the present study was to observe the effect of repeated subcutan eous (sc) injections of low doses of ketamine for the treatment of acute in flammatory pain in a complete Freund's adjuvant-induced monoarthritic pain model in rats. The results show: (1) sc injection of ketamine at a dose of 2 mg.kg(-1) or 10 mg.kg(-1) produced significant analgesia (P<0.01) in arth ritic rats starting from the 2nd week and 3rd week, respectively. (2) Repea ted administration of ketamine produced a significant reduction of the circ umference of the arthritic ankle (P<0.05 and P<0.01 with different doses). (3) The body weight of the rats was not affected by continuous administrati on of ketamine for 4 weeks. No abnormal locomotor behavior was observed (It was concerned but not systemically evaluated in this study). The results s uggest that repeated sc injection of ketamine for 4 weeks significantly red uce inflammatory pain in monoarthritis without notable aversive side effect s. (C) 2000 Elsevier Science Inc. All rights reserved.