When a horse has been in the test barn more than one-and-one-half (1-1/2) hours, a diuretic may be administered by the Official Veterinarian or designee for the purpose of facilitating the collection of a urine sample with permission of the Stewards and the trainer or the trainer's authorized test barn representative. The cost of administration of the diuretic is the responsibility of the owner.
Okla. Admin. Code § 325:45-1-21