Per New York's Public Health Law, Section 3306, ketamine is classified as a Schedule III depressant.  It is a controlled substance, but it is not an opiate.  A veterinarian, in good faith, and in the course of the practice of veterinary medicine only, may prescribe, administer and dispense substances listed in schedules II, III, IV, and V or he may cause them to be administered by a designated agent under his direction and supervision (Public Health Law, Section 3331).