Efficacy of furosemide for prevention of exercise-induced pulmonary hemorrhage in Thoroughbred racehorses.

OBJECTIVE To evaluate the efficacy of furosemide for prevention of exercise-induced pulmonary hemorrhage (EIPH) in Thoroughbred racehorses under typical racing conditions. DESIGN Randomized, placebo-controlled, blinded, crossover field trial. ANIMALS 167 Thoroughbred racehorses. PROCEDURES Horses were allocated to race fields of 9 to 16 horses each and raced twice, 1 week apart, with each of the 2 races consisting of the same race field and distance. Each horse received furosemide (500 mg, IV) before one race and a placebo (saline solution) before the other, with the order of treatments randomly determined. Severity of EIPH was scored on a scale from 0 to 4 after each race by means of tracheobronchoscopy. Data were analyzed by means of various methods of multivariable logistic regression. RESULTS Horses were substantially more likely to develop EIPH (severity score >or= 1; odds ratio, 3.3 to 4.4) or moderate to severe EIPH (severity score >or= 2; odds ratio, 6.9 to 11.0) following administration of saline solution than following administration of furosemide. In addition, 81 of the 120 (67.5%) horses that had EIPH after administration of saline solution had a reduction in EIPH severity score of at least 1 when treated with furosemide. CONCLUSIONS AND CLINICAL RELEVANCE Results indicated that prerace administration of furosemide decreased the incidence and severity of EIPH in Thoroughbreds racing under typical conditions in South Africa.