RSPCA Heartworm Tablet is a monthly heartworm preventive for dogs. The oral treatment prevents heartworm disease in dogs by eliminating the tissue stage of heartworm that infects the dog one month before by mosquitoes. Monthly treatment all year round protects dog from deadly heartworm infection. RSPCA heartworm tablet is easy to dose and highly economical. With no possible side effects, it is approved for adult dogs. RSPCA Heartworm tablets is safe for puppies above 6 weeks old.