The California Horse Racing Board (CHRB) implemented new regulations surrounding the use of the bronchiodilator clenbuterol in Quarter Horse racing at Los Alamitos Race Course, located in Los Alamitos, Calif. The new regulations went into effect on Oct. 14 and were prompted by the increasing use of the substance as a replacement for anabolic steroids.

Clenbuterol is a bronchodilator, and it is used in horses with respiratory problems to relax smooth muscles in the airway, causing the airway to dilate. It also stimulates the activity of the cilia in the trachea, assisting the process of eliminating mucus and microscopic debris.

"The underlying issue is that clenbuterol is a beta-2 agonist and like all drugs in this category has adrenergic (muscle building) effects, especially at higher dosages," explained Rick Arthur, DVM, equine medical director of the CHRB. "Clenbuterol was not being used for the drug’s intended purpose, as a bronchodilator to treat small airway disease. Rather, clenbuterol was being used as a replacement for banned anabolic steroids."

According to a memorandum from Arthur, "Effective Oct. 14, 2011, the authorization for the threshold level for clenbuterol will be suspended in Quarter Horse races at Los Alamitos. Clenbuterol will become similar to other drugs not specifically authorized by the California Horse Racing Board, if the lab detects clenbuterol at any level, it will be a violation