antiprotozoal

An antiprotozoal is a drug used to treat infections caused by protozoa, the single-celled animal-like parasites responsible for diseases such as malaria, amoebic dysentery, giardiasis and toxoplasmosis. Protozoa are eukaryotes, much closer to our own cells than bacteria are, which makes them, like fungi, harder to attack selectively without harming the patient.

These drugs are diverse because protozoa are diverse. Antimalarials such as chloroquine, artemisinins and atovaquone target the malaria parasite at various points of its complex life cycle in red blood cells and the liver; metronidazole and tinidazole are activated inside oxygen-poor parasites like Entamoeba and Giardia to damage their DNA; and other agents tackle Leishmania, trypanosomes and Toxoplasma. Many regimens combine drugs to attack different parasite stages and curb resistance.

Antiprotozoal therapy carries real burdens. Resistance, especially in malaria, has repeatedly forced changes in first-line treatment and now threatens even the artemisinins. Several agents are toxic, and some parasites have dormant tissue forms, such as the liver-stage hypnozoites of certain malarias, that require a separate drug to prevent relapse. Effective control therefore blends the right drug, the right combination, and often vector or transmission control beyond medication alone.