The active ingredient in D-Worm, pyrantel pamoate, has been proven highly effective in removing large roundworms (ascarids toxacara canis and toxascaris leonina) and hookworms (ancylstoma caninum and uncinaria stenocephala) in puppies and dogs. D-Worm also helps prevent the reinfestation of toxocara canis in puppies and adult dogs and in lactating bitches after whelping. No fasting or laxatives required. Approved for use in puppies as young as two weeks old. In clinical tests on dogs of various breeds and ages, pyrantel pamoate caused no side effects.