Can a vet change my dogs meds from a human version to a veterinary version

My dog has been on Selegiline for 2 1/2 years, I get a prescription from them for 6 months, and I get it from a chemist, it has never been a problem. Now vets are saying my dog has to go over to Selgian (veterinary version) at a massive increased cost. Can they do this.

Hello - I'm sorry to say that they may not have much choice.  Here is a blog article by Rebecca Macmillan that you might find interesting (if you can't pick it up from here, try searching for the title using the search-bar in the blog) https://vethelpdirect.com/vetblog/2021/11/21/why-are-vet-medicines-so-expensive/

To be sold by vets for your pet to use, a drug has to undergo massive amounts of testing.  The manufacturers have to prove that it is safe to be sold for that kind of pet in that situation (e.g. for use by dogs to prevent pain in osteoarthritis).  This costs the manufacturer millions of pounds.  In theory, the manufacturer will get the money back from medication sales to the veterinary market, so they get on and do the research.  EXCEPT - if a similar product is already available for the human market - in different packaging and probably a different form - it will probably be cheaper to obtain from the human supply chain, despite not having had to go through all the tests to prove that it is safe for the animals.  This way, veterinary manufacturers are losing out a lot - they do all the work, but then the vets say 'wait a minute - X manufacturer sells somethin similar for humans' and the veterinary drug manufacturer loses out on the profits.

For this reason, legislation exists in the UK that where a manufacturer HAS done all the tests for animals and gone through the licensing process, then their version MUST be prescribed, over any generic form.  It is, after all, safer because the manufacturer has done all the tests to make sure that the product is safe.  This can feel frustrating from our end - we really WANT to offer 'cheap' alternatives where they exist and clients can't afford them.  Indeed, historically, vets have sometimes ignored this rule.

However, to my understanding, the veterinary cascade still stands and veterinary surgeons have no choice but to follow it.

It is a legal and professional matter,