Tri-Heart Plus - Chewable Worm Prevention Tablet For Large Dogs 51-100LB (Brown) - 6TABSDogs of any age, even older dogs, can become infected with heartworms, roundworms or hookworms. Tri Heart Plus chewable tablets contain a proven combination of ingredients to protect your dog and ensure your complete peace of mind. Chewable tablets containing ivermectin and pyrantel. For use in dogs to prevent canine heartworm disease by eliminating the tissue stage of heartworm larvae (Dirofilaria immitis) for a month after infection and for the