Analgesic efficacy of intra-articular morphine in experimentally induced radiocarpal synovitis in horses.
OBJECTIVE
To compare the analgesic effect of intra-articular (IA) and intravenous (IV) morphine in horses with experimentally induced synovitis.


METHODS
Eight adult horses.


METHODS
Randomized, observer blinded, double dummy trial with sequential crossover design.


METHODS
Radiocarpal synovitis was induced by IA injection of lipopolysaccharide on two occasions separated by a 3-week washout period. In one study period horses received treatment IA; morphine IA (0.05 mg kg(-1)) plus saline IV and in the other study period they received treatment IV; saline IA plus morphine IV (0.05 mg kg(-1)). Lameness and pain were evaluated repeatedly by two observers throughout each of the two 168-hour study periods. Pain was evaluated by use of a visual analogue scale of pain intensity (VAS) and a composite measure pain scale (CMPS). Comparison of treatments was performed by analysis of variance with repeated measurements. Significance level was set to p < or = 0.05. Inter-observer agreement and agreement between the VAS and CMPS was assessed by use of the Bland-Altman method.


RESULTS
Intra-articular injection of LPS elicited a marked synovitis resulting in lameness and pain. IA morphine resulted in significantly less lameness than IV morphine (p = 0.03). CMPS (p = 0.09) and VAS (p = 0.10) pain scores did not differ significantly between treatments. Inter-observer agreement of the CMPS was classified as good, but only fair for the VAS. Agreement between the two pain scales was considered fair.


CONCLUSIONS
An analgesic effect of IA morphine was demonstrated by significantly reduced lameness scores. The results support the common practice of including IA morphine in a multimodal analgesic protocol after arthroscopic surgery, although further studies in clinical cases are needed. The employed CMPS had good reproducibility, and was easy to use, but may have limited sensitivity at mild intensity pain.
Department of Large Animal Sciences, University of Copenhagen, Højbakkegård Allé 5, Building 8.68. DK-2630 Taastrup, Denmark. cli@life.ku.dk
Casper
C
Lindegaard
Maj H
MH
Thomsen
Stig
S
Larsen
Pia H
PH
Andersen
D000701:Analgesics, Opioid / Q000008:administration & dosage; D000818:Animals; D050824:Carpal Joints; D018592:Cross-Over Studies; D005260:Female; D006734:Horse Diseases / Q000188:drug therapy*; D006736:Horses; D007270:Injections, Intra-Articular / Q000662:veterinary; D007794:Lameness, Animal / Q000188:drug therapy; D008297:Male; D009020:Morphine; D010146:Pain / Q000188:drug therapy / Q000662:veterinary; D013585:Synovitis / Q000188:drug therapy / Q000662:veterinary*
D000701:Analgesics, Opioid; D009020:Morphine