S.D. Codified Laws § 39-18-34.1
The sale, dispensing, shipping, or otherwise making available of a veterinary drug product label containing the legend "Caution: Federal Law restricts this drug to use by or on the order of a licensed veterinarian" shall result from a relationship between the veterinarian and his client or patient. A valid relationship shall exist if the veterinarian has assumed the responsibility for making medical judgments regarding the health of the animal and the need for medical treatment, and the client has agreed to follow the instructions of the veterinarian; and if there is sufficient knowledge of the animal by the veterinarian to initiate at least a general or preliminary diagnosis of the medical condition of the animal and the veterinarian is readily available for follow-up in case of adverse reactions or failure of the regimen of therapy.
SDCL 39-18-34.1