Antiparasitic drugs are medications designed to treat infections caused by parasites, which are organisms that live on or in a host and benefit at the host's expense. These drugs target various types of parasites, including protozoa, helminths (worms), and ectoparasites (like lice and ticks). Common examples include metronidazole for protozoan infections and ivermectin for certain worm and ectoparasite infestations. The effectiveness of antiparasitic drugs depends on the type of parasite and the specific drug used. Some drugs work by disrupting the parasite's metabolism or reproduction, while others may enhance the host's immune response. Proper diagnosis and treatment are essential, as misuse can lead to resistance and treatment failure.