re: Do i need to give my dog heartworm prevention medication

Some dogs are naturally (or unnaturally) sensitive to avermectin class drugs; ivermectin being one of them. It's approved for use in people and animals. The alternative medications listed all contain milbemycin oxime or moxidectin (milbemycin b). While classified apart from ivermectin, the milbemycins and avermectins share many structural similarities, as well as mechanism of action. There have been reports of cross-sensitivity in animals with demonstrated reaction to ivermectin, but it's not a certainty. The only thing you can really do is try one of the alternatives .