TEXAS VET NEWS By Dr. Bob Judd, DVM and the Texas Farm Bureau Texas Farm Bureau Radio Network

Today on the program I am going to talk about a drug called clenbuterol that is used in horses.  Clenbuterol is sold under the trade name Ventipulmin and is indicated for use in horses with breathing problems.  The most common use is with a respiratory condition called heaves, which is also called chronic obstructive pulmonary disease.  The reason the drug is helpful in breathing is that it causes relaxation of muscles that line the airways.  Relaxations of the muscles allow the airways to get larger or dilate and increase the amount of air a horse can take in on each breath. 

Because the drug increases oxygen to the lungs, it has also been used illegally in performance horses because some people believe it may make them run faster and perform better if they can get more oxygen.  To determine if clenbuterol was effective in increasing performance, several studies have been performed.  Dr. Michael Davis from Oklahoma State reviewed this drug and it appears that in healthy horses, clenbuterol does not increase lung function.  The drug was given intravenously to racehorses and oxygen levels were found to be no higher than in horses that did not receive it.  Although it appears to help horses with diseased lungs, it does not seem to help healthy horses.  Also, clenbuterol has an effect on muscle function and causes horses to get tired more quickly than horses not on the drug.  It has also been shown that clenbuterol given long term could cause decreases in heart function, performance, exercise capacity, and the horse’s ability to recover from exercise.  Therefore, using clenbuterol in performance horses is not a good idea.     

Date Published: 3/9/2009 11:11:00 AM