Antiprotozoal agents ( ATC code: ATC P01) is a class of pharmaceuticals used in treatment of protozoan infection.
Protozoans have little in common with each other (for example,
, a Entamoeba histolytica unikont eukaryotic organism, is less closely related to , a Naegleria fowleri bikont eukaryotic organism, than it is to , which belongs to the unikont phylogenetic group) and so agents effective against one Homo sapiens pathogen may not be effective against another.
They can be grouped by mechanism
or by organism.  Recent papers have also proposed the use of  viruses to treat infections caused by protozoa. 
Antiprotozoals are used to treat protozoal infections, which include
amebiasis, giardiasis, cryptosporidiosis, microsporidiosis, malaria, babesiosis, trypanosomiasis, Chagas disease, leishmaniasis, and toxoplasmosis. Currently, many of the treatments for these infections are limited by their toxicity. 
Once upon a time
protists were considered protozoans, but of late the categorization of unicellar organisms has undergone rapid development, however in literature, including scientific, there tends to persist the usage of the term antiprotozoal when they really mean anti-protist. Protists are a supercategory of eukaryota which includes protozoa.
The mechanisms of antiprotozoal drugs differ significantly drug to drug. For example, it appears that
eflornithine, a drug used to treat trypanosomiasis, inhibits ornithine decarboxylase, while the aminoglycoside antibiotic/antiprotozoals used to treat leishmaniasis are thought to inhibit protein synthesis.
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