Infections caused by Trypanosoma brucei, Trypanosoma cruzi, Leishmania spp., Entamoeba
histolytica, Giardia lamblia, Plasmodium spp., and Trichomonas vaginalis, are part of a large
list of human parasitic diseases. Together, they cause more than 500 million infections per year.
These protozoa parasites affect both low- and high-income countries and their pharmacological
treatments are limited. Therefore, new and more effective drugs in preclinical development could
improve overall therapy for parasitic infections even when their mechanisms of action are unknown.
In this review, a number of heterocyclic compounds (diamidine, guanidine, quinoline, benzimidazole,
thiazole, diazanaphthalene, and their derivatives) reported as antiprotozoal agents are discussed
as options for developing new pharmacological treatments for parasitic diseases.