Like many other animal medicines technically it's a prescription product but that doesn't mean it has to be prescribed by a vet. Suppliers have to have what they call a SQP or "suitably qualified person" on the premises when the product is sold whose job it is to check that you are buying the correct product and that you know what you're doing. That is why if you buy online you should be phoned to check. In fact if they don't phone you they're breaking the law.