The California Horse Racing Board (CHRB), in an effort to curb "apparently indiscriminate use" of thyroid medications, has issued new instructions to veterinarians and horsemen for prescribing, dispensing, and labeling thyroid hormones.

The efforts are to ensure that those involved are in compliance with CHRB regulations. An advisory May 12 points out that all thyroxine within CHRB enclosures must be prescribed by a CHRB-licensed veterinarian for a specific horse and condition. In addition, the medication must be properly labeled in compliance with federal and state laws and CHRB regulations. Horse owners are encouraged to review their veterinary bills and consult with their veterinarians if thyroxine has been prescribed to any of their horses.

The horse, diagnosis, dosage, and estimated last administration date must be reported to the CHRB official veterinarian by practicing vets. The administration of thyroxine or thyroid hormones to horses must be reported by trainers. Any thyroxine or thyroid hormones or thyroid hormone analogs found within the racing enclosure and not properly labeled will be confiscated as contraband.

Veterinarians prescribe thyroxine to treat hypothyroid conditions and, in some cases, to assist in weight loss