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Antiparasitics are a class of medications which are indicated for the treatment of parasitic diseases, such as those caused by helminths,^[1] amoeba,^[2] ectoparasites, parasitic fungi,^[3] and protozoa,^[1] among others. Antiparasitics target the parasitic agents of the infections by destroying them or inhibiting their growth;^[4] 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.^[4] Overuse or misuse of antiparasitics can lead to the development of antimicrobial resistance.

Broad-Spectrum antiparasitics, analogous to broad-spectrum antibiotics for bacteria, are antiparasitic drugs with efficacy in treating a wide range of parasitic infections caused by parasites from different classes.

Types

Broad-spectrum

Nitazoxanide^[5]^[6]^[7]^[8]

Antiprotozoals

Melarsoprol (for treatment of sleeping sickness caused by Trypanosoma brucei)
Eflornithine (for sleeping sickness)
Metronidazole (for vaginitis caused by Trichomonas)
Tinidazole (for intestinal infections caused by Giardia lamblia)
Miltefosine (for the treatment of visceral and cutaneous leishmaniasis, currently undergoing investigation for Chagas disease)

Antihelminthic

Antinematodes

Ancylostoma caninum, a type of hookworm, attached to the intestinal mucosa.

Mebendazole (for most nematode infections)
Pyrantel pamoate (for most nematode infections)
Thiabendazole (for roundworm infections)
Diethylcarbamazine (for treatment of Lymphatic filariasis)
Ivermectin (for prevention of river blindness)

Anticestodes

Niclosamide (for tapeworm infections)
Praziquantel (for tapeworm infections)
Albendazole (broad spectrum)

Antitrematodes

[Praziquantel]

Antiamoebics

Antifungals

Fumagillin (for microsporidiosis)^[3]^[9]

Medical uses

Antiparasitics treat parasitic diseases, which impact an estimated 2 billion people.^[1]

Administration

Antiparastics may be given via a variety of routes depending on the specific medication, including oral, topical, and intravenous.^[4]

Resistance to antiparasitics has been a growing concern, especially in veterinary medicine. The Egg hatch assay can be used to determine whether a parasite causing an infection has become resistant to standard drug treatments.^[10]

Drug development history

Early antiparasitics were ineffective, frequently toxic to patients, and difficult to administer due to the difficulty in distinguishing between the host and the parasite.^[4]

Between 1975 and 1999 only 13 of 1,300 new drugs were antiparasitics, which raised concerns that insufficient incentives existed to drive development of new treatments for diseases that disproportionately target low-income countries. This led to new public sector and public-private partnerships (PPPs), including investment by the Bill and Melinda Gates Foundation. Between 2000 and 2005, twenty new antiparasitic agents were developed or in development.^[11] Metal-containing compounds are the subject of another avenue of approach.^[12]

Research

In the last decades, triazolopyrimidines and their metal complexes have been looked at as an alternative drug to the existing commercial antimonials, searching for a decrease in side effects and the development of parasite drug resistance.^[13]

References

^ ^a ^b ^c Kappagoda, Shanthi; Singh, Upinder; Blackburn, Brian G. (2011). "Antiparasitic Therapy". Mayo Clin. Proc. 86 (6): 561–583. doi:10.4065/mcp.2011.0203. PMC 3104918. PMID 21628620.
^ Kusrini E, Hashim F, Azmi WN, Amin NM, Estuningtyas A (2016). "A novel antiamoebic agent against Acanthamoeba sp. – A causative agent for eye keratitis infection". Spectrochimica Acta Part A: Molecular Spectroscopy. 153: 714–21. Bibcode:2016AcSpA.153..714K. doi:10.1016/j.saa.2015.09.021. PMID 26474244.
^ ^a ^b Molina JM, Tourneur M, Sarfati C, et al. (June 2002). "Fumagillin treatment of intestinal microsporidiosis". N. Engl. J. Med. 346 (25): 1963–9. doi:10.1056/NEJMoa012924. PMID 12075057.
^ ^a ^b ^c ^d "ANTIPARASITICS". Purdue University Cytology Laboratories. Purdue Research Foundation. Retrieved 2015-08-30.
^ Di Santo N, Ehrisman J (2013). "Research perspective: potential role of nitazoxanide in ovarian cancer treatment. Old drug, new purpose?". Cancers (Basel). 5 (3): 1163–1176. doi:10.3390/cancers5031163. PMC 3795384. PMID 24202339. Nitazoxanide [NTZ: 2-acetyloxy-N-(5-nitro-2-thiazolyl)benzamide] is a thiazolide antiparasitic agent with excellent activity against a wide variety of protozoa and helminths. ... Nitazoxanide (NTZ) is a main compound of a class of broad-spectrum anti-parasitic compounds named thiazolides. It is composed of a nitrothiazole-ring and a salicylic acid moiety which are linked together by an amide bond ... NTZ is generally well tolerated, and no significant adverse events have been noted in human trials [13]. ... In vitro, NTZ and tizoxanide function against a wide range of organisms, including the protozoal species Blastocystis hominis, C. parvum, Entamoeba histolytica, G. lamblia and Trichomonas vaginalis [13]
^ White CA (2004). "Nitazoxanide: a new broad spectrum antiparasitic agent". Expert Rev Anti Infect Ther. 2 (1): 43–9. doi:10.1586/14787210.2.1.43. PMID 15482170. S2CID 219184877.
^ Hemphill A, Mueller J, Esposito M (2006). "Nitazoxanide, a broad-spectrum thiazolide anti-infective agent for the treatment of gastrointestinal infections". Expert Opin Pharmacother. 7 (7): 953–64. doi:10.1517/14656566.7.7.953. PMID 16634717. S2CID 13436814.
^ Anderson, V. R.; Curran, M. P. (2007). "Nitazoxanide: A review of its use in the treatment of gastrointestinal infections". Drugs. 67 (13): 1947–1967. doi:10.2165/00003495-200767130-00015. PMID 17722965.
^ Lanternier F, Boutboul D, Menotti J, et al. (February 2009). "Microsporidiosis in solid organ transplant recipients: two Enterocytozoon bieneusi cases and review". Transpl Infect Dis. 11 (1): 83–8. doi:10.1111/j.1399-3062.2008.00347.x. PMID 18803616. S2CID 205423324.
^ Sargison, Neil (2009-01-26). Sheep Flock Health: A Planned Approach. John Wiley & Sons. ISBN 9781444302608.
^ Pink, Richard; Hudson, Alan; Mouries, Marie-Annick; Bendig, Mary (September 2005). "Opportunities and Challenges in Antiparasitic Drug Discovery". Nature. 4 (9): 727–740. doi:10.1038/nrd1824. PMID 16138106. S2CID 19379800.
^ Gambino, Dinorah; Otero Á, Lucía (2019-01-14). "Metal Compounds in the Development of Antiparasitic Agents: Rational Design from Basic Chemistry to the Clinic". Metal Ions in Life Sciences. 19: 331–357. doi:10.1515/9783110527872-019. ISBN 978-3-11-052787-2. ISSN 1559-0836. PMID 30855114.
^ Review (2017). "Leishmanicidal and Trypanocidal Activity of Metal Complexes with 1,2,4-Triazolo[1,5-a]pyrimidines: Insights on their Therapeutic Potential against Leishmaniasis and Chagas Disease". Curr. Med. Chem. 24 (25): 2796–2806. doi:10.2174/0929867324666170516122024. PMID 28521698.