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Antiprotozoal agents (ATC code: ATC P01) is a class of pharmaceuticals used in treatment of protozoan infection.


A paraphyletic group, protozoans have little in common with each other. For example, Entamoeba histolytica , a unikont eukaryotic organism, is more closely related to Homo sapiens (humans), which also belongs to the unikont phylogenetic group, than it is to Naegleria fowleri , a "protozoan" bikont. As a result, agents effective against one pathogen may not be effective against another.

Antiprotozoal agents can be grouped by mechanism [1] or by organism. [2] Recent papers have also proposed the use of viruses to treat infections caused by protozoa. [3] [4]

Medical Uses

Antiprotozoals are used to treat protozoal infections, which include amebiasis, giardiasis, cryptosporidiosis, microsporidiosis, malaria, babesiosis, trypanosomiasis, Chagas disease, leishmaniasis, and toxoplasmosis. [5] Currently, many of the treatments for these infections are limited by their toxicity. [6]

Outdated terminology

Protists were once 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. [7]


Related Research Articles

Parasitic disease Medical condition

A parasitic disease, also known as parasitosis, is an infectious disease caused or transmitted by a parasite. Many parasites do not cause diseases as it may eventually lead to death of both organism and host. Parasites infecting human beings are called human parasites. Parasitic diseases can affect practically all living organisms, including plants and mammals. The study of parasitic diseases is called parasitology.

Trypanosomiasis Medical condition

Trypanosomiasis or trypanosomosis is the name of several diseases in vertebrates caused by parasitic protozoan trypanosomes of the genus Trypanosoma. In humans this includes African trypanosomiasis and Chagas disease. A number of other diseases occur in other animals.


Suramin is a medication used to treat African sleeping sickness and river blindness. It is the treatment of choice for sleeping sickness without central nervous system involvement. It is given by injection into a vein.


Melarsoprol is a medication used for the treatment of sleeping sickness. It is specifically used for second-stage disease caused by Trypanosoma brucei rhodesiense when the central nervous system is involved. For Trypanosoma brucei gambiense, eflornithine or fexinidazole is usually preferred. It is effective in about 95% of people. It is given by injection into a vein.

Mepacrine medication

Mepacrine, also called quinacrine or by the trade name Atabrine, is a medication with several uses. It is related to chloroquine and mefloquine. Although formerly available from compounding pharmacies, as of August 2020 it is unavailable in the United States.


Eflornithine, sold under the brand name Vaniqa among others, is a medication used to treat African trypanosomiasis and excessive hair growth on the face in women. Specifically it is used for the 2nd stage of sleeping sickness caused by T. b. gambiense and may be used with nifurtimox. It is used by injection or applied to the skin.

Virotherapy is a treatment using biotechnology to convert viruses into therapeutic agents by reprogramming viruses to treat diseases. There are three main branches of virotherapy: anti-cancer oncolytic viruses, viral vectors for gene therapy and viral immunotherapy. These branches use three different types of treatment methods: gene overexpression, gene knockout, and suicide gene delivery. Gene overexpression adds genetic sequences that compensate for low to zero levels of needed gene expression. Gene knockout uses RNA methods to silence or reduce expression of disease-causing genes. Suicide gene delivery introduces genetic sequences that induce an apoptotic response in cells, usually to kill cancerous growths. In a slightly different context, virotherapy can also refer more broadly to the use of viruses to treat certain medical conditions by killing pathogens.


Miltefosine, sold under the trade name Impavido among others, is a medication mainly used to treat leishmaniasis and free-living amoeba infections such as Naegleria fowleri and Balamuthia mandrillaris. This includes the three forms of leishmaniasis: cutaneous, visceral and mucosal. It may be used with liposomal amphotericin B or paromomycin. It is taken by mouth.

Antiparasitics are a class of medications which are indicated for the treatment of parasitic diseases, such as those caused by helminths, amoeba, ectoparasites, parasitic fungi, and protozoa, among others. Antiparasitics target the parasitic agents of the infections by destroying them or inhibiting their growth; they are usually effective against a limited number of parasites within a particular class. Antiparasitics are one of the antimicrobial drugs which include antibiotics that target bacteria, and antifungals that target fungi. They may be administered orally, intravenously or topically.


Nitazoxanide, sold under the brand name Alinia among others, is a broad-spectrum antiparasitic and broad-spectrum antiviral medication that is used in medicine for the treatment of various helminthic, protozoal, and viral infections. It is indicated for the treatment of infection by Cryptosporidium parvum and Giardia lamblia in immunocompetent individuals and has been repurposed for the treatment of influenza. Nitazoxanide has also been shown to have in vitro antiparasitic activity and clinical treatment efficacy for infections caused by other protozoa and helminths; evidence as of 2014 suggested that it possesses efficacy in treating a number of viral infections as well.

Crithidia fasciculata is a species of parasitic excavates. C. fasciculata, like other species of Crithidia have a single host life cycle with insect host, in the case of C. fasciculata this is the mosquito. C. fasciculata have low host species specificity and can infect many species of mosquito.

Blastocystosis Medical condition

Blastocystosis refers to a medical condition caused by infection with Blastocystis. Blastocystis is a protozoal, single-celled parasite that inhabits the gastrointestinal tracts of humans and other animals. Many different types of Blastocystis exist, and they can infect humans, farm animals, birds, rodents, amphibians, reptiles, fish, and even cockroaches. Blastocystosis has been found to be a possible risk factor for development of irritable bowel syndrome.

Protozoan infection Parasitic disease caused by a protozoan

Protozoan infections are parasitic diseases caused by organisms formerly classified in the Kingdom Protozoa. They are usually contracted by either an insect vector or by contact with an infected substance or surface and include organisms that are now classified in the supergroups Excavata, Amoebozoa, SAR, and Archaeplastida.

Protist Eukaryotic organisms that are not animals, plants or fungi

A protist is any eukaryotic organism that is not an animal, plant, or fungus. While it is likely that protists share a common ancestor, the exclusion of other eukaryotes means that protists do not form a natural group, or clade. Therefore, some protists may be more closely related to animals, plants, or fungi than they are to other protists; however, like algae, invertebrates, or protozoans, the grouping is used for convenience. The study of protists is termed protistology.

Protozoa Single-celled eukaryotic organisms that feed on organic matter

Protozoa is an informal term for a group of single-celled eukaryotes, either free-living or parasitic, that feed on organic matter such as other microorganisms or organic tissues and debris. Historically, protozoans were regarded as "one-celled animals", because they often possess animal-like behaviours, such as motility and predation, and lack a cell wall, as found in plants and many algae.

Fexinidazole is a medication used to treat African trypanosomiasis cause by Trypanosoma brucei gambiense. It is effective against both first and second stage disease. Some evidence also supports its use in Chagas disease. It is taken by mouth.

In biology, a pathogen in the oldest and broadest sense, is any organism that can produce disease. A pathogen may also be referred to as an infectious agent, or simply a germ.

The biological classification system of life introduced by British zoologist Thomas Cavalier-Smith involves systematic arrangements of all life forms on earth. Following and improving the classification systems introduced by Carl Linnaeus, Ernst Haeckel, Robert Whittaker, and Carl Woese, Cavalier-Smith's classification attempts to incorporate the latest developments in taxonomy. His classification has been a major foundation in modern taxonomy, particularly with revisions and reorganisations of kingdoms and phyla.


GNF6702 is the name for a broad-spectrum antiprotozoal drug invented by researchers working at the Genomics Institute of the Novartis Research Foundation in 2013, with activity against leishmaniasis, Chagas disease and sleeping sickness. These three diseases are caused by related kinetoplastid parasites, which share similar biology. GNF6702 acts as allosteric proteasome inhibitor which was effective against infection with any of the three protozoal diseases in mice, while having little evident toxicity to mammalian cells.

Anti-protist or antiprotistal refers to an anti-parasitic and anti-infective agent which is active against protists. Unfortunately due to the long ingrained usage of the term antiprotozoal, the two terms are confused, when in fact protists are a supercategory. Therefore, there are protists that are not protozoans. Beyond "animal-like" protozoans, protists also include the "plant-like" (autotrophic) protophyta and the "fungi-like" saprophytic molds. In current biology, the concept of a "protist" and its three subdivisions has been replaced.


  1. Cynthia R. L. Webster (15 June 2001). Clinical pharmacology. Teton NewMedia. pp. 86–. ISBN   978-1-893441-37-8 . Retrieved 2 May 2010.
  2. Anthony J. Trevor; Bertram G. Katzung; Susan B. Masters (11 December 2007). Katzung & Trevor's pharmacology: examination & board review. McGraw-Hill Professional. pp. 435–. ISBN   978-0-07-148869-3 . Retrieved 2 May 2010.
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  4. Hyman, P.; Atterbury, R.; Barrow, P. (2013). "Fleas and smaller fleas: Virotherapy for parasite infections". Trends in Microbiology. 21 (5): 215–220. doi:10.1016/j.tim.2013.02.006. PMID   23540830.
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  6. Graebin, C.; Uchoa, F.; Bernardes, L.; Campo, V.; Carvalho, I.; Eifler-Lima, V. (1 October 2009). "Antiprotozoal Agents: An Overview". Anti-Infective Agents in Medicinal Chemistry. 8 (4): 345–366. doi:10.2174/187152109789760199. ISSN   1871-5214.
  7. CREEK, DARREN J.; BARRETT, MICHAEL P. (9 January 2017). "Determination of antiprotozoal drug mechanisms by metabolomics approaches". Parasitology. 141 (1): 83–92. doi:10.1017/S0031182013000814. ISSN   0031-1820. PMC   3884841 . PMID   23734876.