Antiprotozoals

Antiprotozoals are medicines used to treat infections caused by protozoa, a diverse group of single-celled parasites. They are employed against diseases such as malaria (Plasmodium species), amoebiasis, giardiasis, trichomoniasis, toxoplasmosis, leishmaniasis, and African or American sleeping sickness and related illnesses. Treatments may target systemic tissue stages, luminal intestinal forms, or both, and regimens often combine several agents to improve efficacy and limit resistance.

Drug classes and examples are varied. Antimalarials include chloroquine, quinine, mefloquine, primaquine for radical cure, and artemisinin-based therapies (artemether, artesunate) often given with partner drugs (ACTs). Other agents such as atovaquone–proguanil and piperaquine are used in malaria control. Nitroimidazoles, notably metronidazole and tinidazole, treat anaerobic protozoa causing amoebiasis, giardiasis, and trichomoniasis. Nitazoxanide treats Giardia and Cryptosporidium infections. Pyrimethamine–sulfadiazine inhibits folate synthesis and is used for toxoplasmosis, with folate antagonists also employed in combination for other indications. Leishmaniasis is treated with antimonials, amphotericin B formulations, miltefosine, and combinations in certain settings. Trypanosomiasis therapies include various nitro compounds and others such as suramin, pentamidine, melarsoprol, eflornithine, and nifurtimox–eflornithine therapy (NECT) for central nervous system disease. Chagas disease employs benznidazole or nifurtimox. Clindamycin and combination regimens are used in specific toxoplasmosis and other protozoal infections.

Mechanisms vary by agent, including disruption of DNA synthesis or integrity (metronidazole), inhibition of folate metabolism (pyrimethamine), interference with mitochondrial function (atovaquone), or disruption of heme detoxification (artemisinins). Resistance and toxicity are considerations, guiding use, dosing, and, where appropriate, combination therapy.