Anti-protozoal agents: any of antibiotic compounds which exhibit  activity against specific unicelular organisms, and therefore may be used in treatment of protozoan infection.

Protozoans have little in common with each other (for example, Entamoeba histolytica, an unikont eukaryotic organism, is less closely related to Naegleria fowleri, a bikont eukaryotic organism, than it is to Homo sapiens, which belongs to the unikont phylogenetic group) and so agents effective against one pathogen may not be effective against another.{Wikipedia)