I wouldn't even consider withholding heart worm meds from my dog. The likelihood of her suffering a seizure from it is statistically nil. And I've PAID for strays (that followed my dog home) to have their blood cleared of heart worm larvae and it was NOT cheap.There are 90 million dogs in the US. That means the number that have this reaction to those meds are nearly statistically zero. Those meds also prevent very prevalent and deadly diseases. Have you ever seen a dog in the late stages of a heartworm infestation?
Give your dog their Heartworm meds.