Anti-inflammatory effects of topically applied dimethyl sulfoxide gel on endotoxin-induced synovitis in horses

Abstract

Objective - To evaluate the effect of topically applied dimethylsulfoxide (DMSO) on lipopolysaccharide (LPS)-induced synovitis in the mid-carpal joint. Animals - 6 sound, healthy, adult horses (12 carpi). Procedure - In a double-blinded, crossover, paired study with a 1-week washout period, mid-carpal joints were allocated to group 1 (DMSO, n = 6) or group 2 (control, n = 6). Each joint was injected with 1.3 ml (0.0125 ng/dl) of LPS to induce synovitis. For group-1 joints, DMSO gel (15 g; 90%) was applied after injection of LPS and at 12-hour intervals for 60 hours. Joints of group 2 received LPS, but not DMSO gel. All horses were evaluated by serial lameness examinations and synovial fluid analyses (total and differential WBC count and total protein concentration) at 12-hour intervals for 60 hours after LPS injection. Plasma and synovial fluid were obtained at baseline and 36 hours to document presence of DMSO. Results - Mean WBC concentration was significantly (P < 0.05) lower in group-1, compared with group-2 joints, at 24 hours and had a trend to be lower at 36 hours. Mean total neutrophil count was significantly lower in group-1, compared with group-2 joints at 24 hours. In group-1 joints, DMSO was detected by use of gas chromatography in the synovial fluid of 5 of 6 joints and in plasma from 1 of 6 horses. Conclusion - Topically applied DMSO penetrated into synovial fluid in sufficient quantities to be detected and to decrease joint inflammation.