Abstract Detomidine may induce analgesia when admin- istered at peripheral sites, e.g., at joint cavities or around nerves. The purpose of this study was to document the effects of detomidine HCl on biochemical and cytological properties of synovial fluid in horses. Five horses under- went clinical examination for lameness and flexion test to document limb health prior to acceptance to the study. Synovial fluids were taken from both radiocarpal joints, and 20 μg/kg detomidine HCl diluted in 3 ml saline and 3.2 ml saline was injected randomly to joints at day 0. Synovial fluid collection from the joints was performed at days 1, 2, and 7 after injection. Twenty-five-meter straight-line trot was used to assess lameness at days 1, 2, and 7 post detomidine injection. Total white blood cells (WBC), cytological examination, total protein, specific gravity, alkaline phosphates (ALP), aspartate aminotransferase (AST), alanine aminotransferase (ALT), creatine phospho- kinase (CK), glucose, and quality of mucin clot were measured. No detectable lameness was observed through- out the study. Mucin clot quality test revealed no significant differences between various sampling times (P>0.05). Cytological examination of synovial fluid of horses showed no significant differences between various sampling times for total WBC and also various types of leukocytes (P>0.05). The amount of total protein, specific gravity, ALP, CK, glutamic–pyruvic transaminase (GPT), and glucose revealed no significant differences between varioussampling times between test and control groups (P>0.05). The only significant difference was seen at day 7 for AST between test and control groups (P<0.05).

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