If they accept something like PayPal, it should be pretty trivial to get your money back if they won't provide it. I wouldn't bother if there's no credit card / PayPal - I can't tell but it almost all seems to be wire transfer, which is the hallmark of a scam site.
That stuff is for IV administration, by the way. But if the N was legit, that would be a pretty minor obstacle.
However, I had a search and I found several 'Spanish vet stores' selling this. What I suspect is going on is that these are sham storefronts, judging by the quality of the sites and the lack of specific information related to the stores (other than contact details) on them. That none of them mention regulations is a giveaway pretty much. It's a common scam tactic, they all tend to be populated with pretty similar databases of cheap branded goods and then it doesn't take much time to put up a site made by some ecommerce template. They don't seem to be customised or even have much set up like a domain-specific email or non-default FAQ - weird for a site that would be trying to sell things, never mind highly regulated, niche things.
(Search something like 'site:.es exagon solucion' - if you vary your search terms you can find ones that aren't even in Spanish but still use the Spanish .es TLD. Spanish example:
https://distribuidorveterinario.es/ - it even has a Facebook linking to a maybe real veterinary pharmacy storefront even, but it's not used by anyone. Anyway it's not clear that they own the business and their branding is totally different.)
If you're in Spain, some of them do have contact numbers/addresses up, if you're desperate.
