When must furosemide be administered to a horse?

Furosemide, commonly known by its brand name Lasix, is a medication frequently used in racehorses to prevent exercise-induced pulmonary hemorrhage (EIPH). It is important to administer furosemide in a timely manner to ensure it is effective during competition. The correct timing for administration is no later than four hours before post time. This allows sufficient time for the medication to take effect and to clear the horse's system adequately before it competes.

Administering furosemide too late, such as right before the race or after the race, would not provide the intended benefits for managing EIPH during the race. Additionally, administering it too early, such as the day before, may not align with the immediate therapeutic needs during the race itself. Therefore, the guideline to administer it up to four hours before post time strikes a balance that helps ensure the horse is properly treated and can perform optimally.