Last winter and part of spring that I spent in Mexico with all the tummy, fungus, etc issues we had (and thankfully it all went well
)
I noticed that most vets will write a prescription for you. The vet where I took them would calculate with human grade brands the right dose, depending on their size, age and weight. Then you go to the pharmacy (human) and show the prescrpition and they get you the meds no one ever questioned me it's like "whatever", everyday stuff
Only things you get at the clinic are things like vitamins, flea and ticks or very specific medications but most by far prescribed are the same as for humans.
I read on this thread that SCM's cat has even a profile in London Drugs so it shouldn't be a problem either... In theory.