Here’s an issue for you: Ever been to the veterinary hospital to pick up some heartworm medication and been told it’s time for a test before they can sell it to you or script it out? Been denied by the online pharmacy based on your veterinarian’s unwillingness to offer a prescription until she sees you again?


It happens all the time. Owners want a prescription product so they can responsibly protect their pets and they’re told that it requires a valid veterinarian-client-patient relationship (VCPR). That’s when you say, “What the heck is that and what does it have to do with a simple batch of heartworm meds?”


A VCPR concerns a special relationship rule that keeps veterinarians from dispensing any prescription product if we haven’t physically treated your pet in over a year. But that’s not all we require to write out a prescription for this stuff. Most of us also demand that you subject your pet to a heartworm test.


The rationale, so you understand, is that sometimes when we administer these “filaricide” products to dogs infected with the larval forms of the heartworm parasite (microfilaria) they can suffer a deadly reaction to the sudden death of worms. That’s what keeps these products from being sold over the counter without a recent heartworm test.


Some veterinarians take this regulation to a higher level. If it’s clear that you haven’t refilled your prescription in a timely fashion (so that it’s evident your pet has missed a month or more of these every-30-day meds), they’ll deny you unless you get another blood test. Stickler city!


But a small but vocal contingent of veterinarians disagrees with these stringent requirements. After all, they say, reactions to microfilaria are an overblown rarity relied upon by veterinarians and drug companies so they can maintain their Rx requirement and drive drug sales along with veterinary visits.


Considering that the risk of heartworm infection is far, far higher than the risk of a serious reaction to the death of heartworm babies, they argue, does it not behoove us as a profession to accept the reality: OTC sales of heartworm meds should be the norm if we want to save lives and prevent disease.


That’s even more obvious, they say, given that some newer generation heartworm medications don’t offer this side effect at all. Revolution, Pfizer’s answer to heartworm, fleas, ticks, mange, ear mites and intestinal parasite infection, does not cause the kind of sudden death of microfilaria that would precipitate a potentially catastrophic reaction. Why restrict its usage based on a prescription only classification?


More evidence for this approach revolves around some veterinarians’ recommendation that heartworm positive dogs should be treated first with heartworm meds to sterilize the female heartworms and cause a slow die-off of the babies (you can read a scientific discussion of this and the filaricide reactions on the American Heartworm Society's website). 


Truth is, I see these veterinarians’ point of view very clearly. Yet my in-hospital colleagues don’t share my enthusiasm for this approach. Our hospital policy is such that if you miss a month your dog is re-tested. Cats get a pass since there’s little evidence of dangerous filaricide reactions. But dogs? No way, they say. Come on back for a test.


Sure, I see the need for a valid VCPR with yearly visits and annual heartworm testing, but beyond that...? How careful need we really be?