Review of furosemide in horse racing: its effects and regulation

Abstract

Furosemide has been used empirically and has been legally approved for many years by the US racing industry for the control of exercise-induced pulmonary haemorrhage (EIPH) or bleeding. Its use in horses for this purpose is highly controversial and has been criticized by organizations outside and inside of the racing industry. This review concentrates on its renal and extra-renal actions and the possible relationship of these actions to the modification of EIPH and changes in performance of horses. The existing literature references suggest that furosemide has the potential of increasing performance in horses without significantly changing the bleeding status. The pulmonary capillary transmural pressure in the exercising horse is estimated to be over 100 mmHg. The pressure reduction produced by the administration of furosemide is not of sufficient magnitude to reduce transmural pressures within the capillaries to a level where pressures resulting in rupture of the capillaries, and thus haemorrhage, would be completely prevented. This is substantiated by clinical observations that the administration of furosemide to horses with EIPH may reduce haemorrhage but does not completely stop it. The unanswered question is whether the improvement of racing times which have been shown in a number of studies are due to the reduction in bleeding or to other actions of furosemide. This review also discusses the difficulties encountered in furosemide regulation, in view of its diuretic actions and potential for the reduction in the ability of forensic laboratories to detect drugs and medications administered to a horse within days or hours before a race. Interactions between nonsteroidal anti-inflammatory drugs (NSAIDs) and furosemide have also been examined, and the results suggest that the effects of prior administration of NSAID may partially mitigate the renal and extra-renal effects which may contribute to the effects of furosemide on EIPH.

Is improved high speed performance following frusemide administration due to diuresis‐induced weight loss or reduced severity of exercise‐induced pulmonary haemorrhage?

“…Prerace administration of frusemide is regarded as the most effective way to reduce the severity of EIPH; and i.v. injection has been associated with a significant improvement in racing times of Thoroughbreds and Standardbreds (Soma and Uboh 1998;Geor et al 2001). It has been presumed, but not demonstrated, that this improvement is linked to a reduction in the severity of EIPH.…”

Pharmacokinetics and Pharmacodynamics of Furosemide after Oral Administration to Horses

“…5 The most common use of furosemide in the horse, however, is to attempt to decrease severity of exercise-induced pulmonary hemorrhage in racing horses, although the rationale and effects of furosemide in this context are highly debated. 6,7 Furosemide is routinely administered by injection IV or IM (250-500 mg q6-8h). 8 Furosemide is effective after administration PO in other species, and administration PO is often suggested as an alternative to parenteral administration in long-term treatment of horses with congestive heart failure 2,9,10 ; however, documentation of its pharmacokinetic or pharmacodynamic characteristics after administration PO has not been reported.…”

Veterinary Medicines and Competition Animals: The Question of Medication Versus Doping Control

“…However, a recent investigation showed that furosemide was able to decrease the incidence and severity of EIPH in thoroughbreds (Hinchcliff et al 2009). It should be stressed that epidemiological surveys have provided evidence that furosemide may improve racing performance (Soma and Uboh 1998). In horses, furosemide decreased the oxygen debt and the rate of blood lactate accumulation.…”

“…In horses, furosemide decreased the oxygen debt and the rate of blood lactate accumulation. This effect can be reversed by adding to the horse a weight compensating for the loss of body weight due to the diuresis produced by furosemide (approximately 16 kg), suggesting that changes in performance observed in bleeder horses after a furosemide treatment is due to a small reduction in body weight and not to a selective pharmacological action on bleeding mechanisms (Soma and Uboh 1998;Zawadzkas et al 2006). In addition, furosemide is disapproved of because it causes diluted urine, i.e.…”