I've never worked for or met a vet that wouldn't write a script for basically a refill. Try seeing if they'll price match at your vet (most practices down here do, but don't offer it unless you ask). Most likely they'll require you to have the "checkout" screen printed that details the shipping cost. Some add this shipping cost to the final cost.
I've never heard of using the Fish Zole tabs for dogs, I'd just try the above first.
I've never heard of using the Fish Zole tabs for dogs, I'd just try the above first.