Furosemide is used acutely in racehorses and chronically for treatment of edema and
congestive heart failure, but the behavioral effects on horses of chronic administration of
this drug have not been studied. The objectives of this study were to measure salt and
water intake as well as sodium and water losses in ponies treated chronically with furosemide.
The salt and water intake of ponies was measured daily for 3 weeks before and
3 weeks during treatment with furosemide at a dose of 0.5 mg/kg/d. Fecal dry matter was
measured for 9 days before and during furosemide treatment by collecting a fecal sample
from each pony’s stall and drying it overnight in a 100C oven. Urine volume and urine
sodium content were measured daily for three consecutive days during pretreatment,
treatment, and post-treatment periods so that sodium and water status could be calculated.
Sodium chloride intake increased in ponies treated daily with furosemide from 7.9
2.2 (standard error of the mean) to 20.3 2.4 g/d and was significantly higher than control
for all weeks of treatment (P < .03). Water intake was also significantly increased from 8.9
1 during the control period to 11 0.7 kg/d during furosemide treatment (P < .001), and
the ponies drank more water than they lost. Urine volume and urine sodium concentrations
increased significantly during treatment with the diuretic, whereas urinary potassium
and calcium concentrations decreased.