Dose-Finding Study for Intraarticular Treatment With Stanozolol in Horses

Recent reports accounted for the intraarticular (IA) use of the stanozolol in the horse as a disease-modifying drug without any previous specific indication concerning the minimal dosage effective in the horse, avoiding or limiting anabolic consequences. The objective was (1) to evaluate possible adverse reactions after IA administration of three different dosages (1, 2.5, and 5 mg) of stanozolol in metacarpophalangeal joints of lame horses; (2) to evaluate its clinical and pharmacologic effects; and (3) to find out the minimal drug dose that can produce a one grade reduction of lameness in the American Association of Equine Practitioner (AAEP) lameness scale in at least 80% of the treated animals. Twenty-four horses with acute lameness of 2/5 (AAEP scale) due to osteoarthritis of the fetlock joint were included in the study. The animals were randomly divided in four groups that received every 7 days placebo or 1, 2.5, and 5 mg of stanozolol, respectively, until a one grade decrease of lameness was reached. No noticeable adverse reactions were observed. In two horses of six (33.3%), grouped in stanozolol 1 mg (STN 1), 2.5 mg (STN 2.5), and 5 mg (STN 5), the lameness score decreased after the first injection. During the evaluation after the second injection, five horses of six (83.33%) in the group STN 5 showed reduced or no lameness, whereas the reduction in lameness observed in the STN 1 and STN 2.5 groups was in four of six (66.6%). In conclusion, two IA treatments with 5 mg of stanozolol produce a reduction of one grade lameness in early osteoarthritis in horses.