I did the heart worm deal and my dog basically came out of his skin,..was eating himself like he was flea infested. Next time around, same thing,..I told the vet no more. Well it wasn't maybe 7 year til I understood why. My dog got hit by a car. He went to the vet, vet says looks good, but let's xray just in case and then the trouble began. They sedate to xray,..an hour later my husband brought home a very big dog, limp and out of it. My husband said should be up and around in an hour or so. I said hmmm, because when they put my Basset hound under for spay, by the time I came back to pick her up, which was within an hour She was up and about and walked out of the vets (long story short...she was already spayed and vet didn't figure it out until she knocked her out,..did I mention we don't use that vet anymore).
So 8 hours later dog is still limp and out of it,..I start googling the meds,..then I decide to add the breed australian shepard mix,...and low and behold,..a genetic mutation in the breed, they should not be sedated as you would normally and then I see the heartworm med issues was not in my head it also reacted to the genetic defect of the australian shepards. My dog was out of it for 2 days, my vet had to come out to the house to help us gurney him outside to manually relieve him,..not only was I scared but I could see the vet was as well. He had never heard of the genetic deal with the aussies, so needless to say we have that noted on Baileys chart and my vet has a new item for his bag of tricks.
For me I give nothing to any of my animals without really weighing the ramifications, I did not blame my vet, but I see for myself we take alot of expert advise for granted that it is what is right and I see it isn't so much. Oh so, heart worms,..we use nothing.