Antiprotozoal

Antiprotozoal agents are drugs used to treat infections caused by protozoa, a diverse group of unicellular organisms that includes Plasmodium, Giardia, Entamoeba, Toxoplasma, Cryptosporidium, Trypanosoma, and Leishmania. They are used therapeutically for malaria, intestinal protozoan infections, and tissue infections, and may be given as treatment or prophylaxis depending on the parasite and disease stage.

Mechanisms of action vary. Some compounds inhibit nucleic acid synthesis or DNA replication (for example, nitroimidazoles such as metronidazole and tinidazole). Others disrupt energy metabolism or mitochondrial function (atovaquone; artemisinin derivatives). Folate synthesis is blocked by pyrimethamine-sulfadiazine. Heme detoxification is inhibited by chloroquine and related drugs in malaria. Some agents interfere with parasite protein synthesis (tetracyclines, clindamycin) and nitazoxanide broadens activity against several anaerobic protozoa.

Representative uses include malaria with artemisinin-based therapies or quinine and chloroquine in sensitive regions; metronidazole or tinidazole for Giardia and Entamoeba; pyrimethamine-sulfadiazine for toxoplasmosis; miltefosine or amphotericin B for leishmaniasis; nitazoxanide for certain Cryptosporidium and Giardia infections.

Challenges include drug resistance, side effects, and limitations in pregnancy safety and pediatric use. Antiprotozoals are typically prescribed based on local parasite species, susceptibility patterns, and patient factors, highlighting the importance of accurate diagnosis and clinical guidelines.