There are some on-line pharmacies out of the country that may let you purchase heartworm meds without a prescription (laws differ). They not only charge a lot, but it is not recommended to by on-line meds as there is a lot of counterfeit stuff out there, you can’t be sure how it has been stored, expiration dates etc,
If anything goes wrong because of the med, the company will have no liability because you did not purchase it from a veterinarian.
The annual Heartworm Disease/Lyme Disease/Ehrlichiosis/Anaplasmosis test is important, I would not recommend skipping it.
per the search engine here:
/forums/search/heartworm+meds/
PS: I would listen to what your veterinarian recommends.
