Here's a refresher on some of the lingo involved in discussing, explaining, and marketing veterinary drugs.
A patented drug is protected by the U.S. Patent and Trademark Office, which means other manufacturers cannot sell the same formulation. Once the patent expires, other companies can produce generic versions. Sometimes these generics are sold under the name of the active ingredient, while others have their own unique brand name, in which case they become a branded generic. Both patented and generic drugs are FDA-approved. The original version of the drug must show efficacy in FDA trials, while the generic version must show bioequivalence to the original.
Both human generics and veterinary generics are available to veterinarians. When a practitioner prescribes any drug, including a human generic, for a purpose other than what the FDA has approved, he or she is using the drug off-label. Over-the-counter, or OTC, drugs do not require a prescription but, like prescription-only drugs, they are still FDA-regulated.
Topical parasiticide products can be patented or generic but they're regulated by the Environmental Protection Agency and not the FDA; therefore they're EPA-registered. A topical parasiticide manufacturer may decide to sell its products OTC or through veterinary-exclusive channels. Sometimes veterinary-exclusive products show up OTC in retail outlets as a result of product diversion into what has become known as the gray market.