The Big, Bad Furosemide: Barrel Racers’ Lasix Questions Answered

Learn about Lasix and its relationship to barrel racing horses.
drawing blood on a horse

Lately, yet another social media battle has taken place over Furosemide, better known as “Lasix,” and whether or not it has a place in the barrel racing community and with barrel racing horses.

We pulled some information from one of our favorite The Money Barrel Podcast interviews with Dr. Melissa Fenn regarding pulmonary problems, EIPH, bleeding, Lasix and more to help shed some light on the simple facts surrounding this popular performance medication.

What is Furosemide, “Lasix,” and why is it used in barrel racing?

A: Lasix is a diuretic used to decrease blood volume and minimize pressure on alveolar capillaries during exercise, particularly to manage Exercise-Induced Pulmonary Hemorrhage (EIPH).

“Lasix is a diuretic,” Dr. Fenn said. “You give it and it helps basically decrease blood volume…By decreasing blood volume, you’re minimizing that pressure that’s put on those tiny little alveolar capillaries.”

Is Lasix considered a good or bad medication in barrel racing?

A: Lasix is considered a necessary medication for managing EIPH, but there may be misconceptions about its usage.

Dr. Fenn emphasizes, “Lasix is the only treatment of all of those that have been evaluated…that has evidence behind its success in managing this condition.”

What are the proper dosing and timing guidelines for administering Lasix?

A: The recommended dose of Lasix typically ranges from 2.5 to 10 mils for a one thousand to eleven hundred pound horse, with an initial dose starting at 3 to 5 mils.

Dr. Fenn advises, “I typically recommend that your average size barrel horse starts at about 3 to 5 mils IV (intravenous) or IM (intramuscular). Another important thing is the timing of when Lasix is supposed to be given. I recommend 4 hours before the race.”

What are the potential risks or side effects of using Lasix?

A: While effective, Lasix is a potent diuretic that must be used carefully to avoid adverse effects.

Dr. Fenn warns, “If it’s not used correctly, it’s either not going to help your problem at all, or it could potentially have some adverse side effects.”

Can Lasix be used as a preventative measure in barrel racing?

A: Lasix can be used preventatively, but consultation with a veterinarian is crucial to assess the horse’s clinical signs and determine the necessity for its use. Dr. Fenn advises, “I guess I would recommend it as a preventative if you’ve had an open and frank conversation with your vet about it first…having those open and candid conversations with them is really the most important step” (source).

What precautions should be taken after administering Lasix?

A: It’s essential to withhold water after giving Lasix to prevent the horse from replenishing the lost fluids, which could diminish the drug’s effectiveness. Dr. Fenn explains, “Once you give the Lasix, you need to withhold water…because, again, it’s a diuretic, so it’s gonna make them pee out and decrease their plasma volume and their blood volume.”

Want to dive deeper? Listen to the full The Money Barrel episode, presented by Gold Buckle Horse Sale.