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Clinical data
Trade namesNiclocide, Fenasal, Phenasal, others[1]
AHFS/Drugs.comMicromedex Detailed Consumer Information
ATC code
CAS Number
PubChem CID
ECHA InfoCard100.000.052 Edit this at Wikidata
Chemical and physical data
Molar mass327.119 g/mol
3D model (JSmol)
Melting point225 to 230 °C (437 to 446 °F)
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Niclosamide, sold under the trade name Niclocide among others, is a medication used to treat tapeworm infestations.[2] This includes diphyllobothriasis, hymenolepiasis, and taeniasis.[2] It is not effective against other worms such as pinworms or roundworms.[3] It is taken by mouth.[2]

Side effects include nausea, vomiting, abdominal pain, constipation, and itchiness.[2] It may be used during pregnancy and appears to be safe for the baby.[2] Niclosamide is in the anthelmintic family of medications.[3] It works by blocking the uptake of sugar by the worm.[4]

Niclosamide was discovered in 1958.[5] It is on the World Health Organization's List of Essential Medicines, the most effective and safe medicines needed in a health system.[6] The wholesale cost in the developing world is about 0.24 USD for a course of treatment.[7] It is not commercially available in the United States.[3] It is effective in a number of other animals.[4]

Side effects[edit]

Side effects include nausea, vomiting, abdominal pain, constipation, and itchiness.[2] Rarely, dizziness, skin rash, drowsiness, perianal itching, or an unpleasant taste occur. For some of these reasons, praziquantel is a preferable and equally effective treatment for tapeworm infestation.[citation needed]

Mechanism of action[edit]

Niclosamide inhibits glucose uptake, oxidative phosphorylation, and anaerobic metabolism in the tapeworm.[8]

Other applications[edit]

Niclosamide's metabolic effects are relevant to wide ranges of organisms, and accordingly it has been applied as a control measure to organisms other than tapeworms. For example, it is an active ingredient in some formulations for killing lamprey larvae,[9] as a molluscide,[10] and as a general purpose piscicide in aquaculture. Niclosamide has a short half-life in water in field conditions; this makes it valuable in ridding commercial fish ponds of unwanted fish; it loses its activity soon enough to permit re-stocking within a few days of eradicating the previous population.[10] Researchers have found that Niclosamide proves effective in killing invasive zebra mussels in cool waters.[11]


Niclosamide, along with oxyclozanide, another anti-tapeworm drug, was found in a 2015 study to display "strong in vivo and in vitro activity against methicillin-resistant Staphylococcus aureus (MRSA)".[12] In addition, niclosamide was found to inhibit the gastric pathogen Helicobacter pylori in vitro and in vivo .[13] A 2016 drug repurposing screening study suggested that niclosamide may inhibit Zika virus replication in vitro.[14]

Niclosamide seems to inhibit the STAT3 signalling pathway which is active in some cancers.[15]


  1. ^ CID 4477 from PubChem
  2. ^ a b c d e f WHO Model Formulary 2008 (PDF). World Health Organization. 2009. pp. 81, 87, 591. ISBN 9789241547659. Archived (PDF) from the original on 2016-12-13.
  3. ^ a b c "Niclosamide Advanced Patient Information -". Archived from the original on 20 December 2016. Retrieved 8 December 2016.
  4. ^ a b Jim E. Riviere; Mark G. Papich (13 May 2013). Veterinary Pharmacology and Therapeutics. John Wiley & Sons. p. 1096. ISBN 978-1-118-68590-7. Archived from the original on 10 September 2017.
  5. ^ Mehlhorn, Heinz (2008). Encyclopedia of Parasitology: A-M. Springer Science & Business Media. p. 483. ISBN 9783540489948. Archived from the original on 2016-12-20.
  6. ^ "WHO Model List of Essential Medicines (19th List)" (PDF). World Health Organization. April 2015. Archived (PDF) from the original on 13 December 2016. Retrieved 8 December 2016.
  7. ^ "Niclosamide". International Drug Price Indicator Guide. Archived from the original on 10 May 2017. Retrieved 1 December 2016.
  8. ^ Weinbach EC, Garbus J (1969). "Mechanism of action of reagents that uncouple oxidative phosphorylation". Nature. 221 (5185): 1016–8. doi:10.1038/2211016a0. PMID 4180173.
  9. ^ Boogaard, Michael A. Delivery Systems of Piscicides "Archived copy" (PDF). Archived (PDF) from the original on 2017-06-01. Retrieved 2017-05-30.
  10. ^ a b Who Specifications And Evaluations. For Public Health Pesticides. Niclosamide []
  11. ^ "Researchers find new methods to combat invasive zebra mussels". The Minnesota Daily. Retrieved 2018-11-19.
  12. ^ Repurposing Salicylanilide Anthelmintic Drugs to Combat Drug Resistant Staphylococcus aureus Archived 2015-05-02 at the Wayback Machine. at PLOS
  13. ^ Tharmalingam N; et al. (2018). "Repurposing the anthelmintic drug niclosamide to combat Helicobacter pylori". Scientific Reports. 8: 3701. doi:10.1038/s41598-018-22037-x. PMC 5829259. PMID 29487357.
  14. ^ Xu, Miao; Lee, Emily M; Wen, Zhexing; Cheng, Yichen; Huang, Wei-Kai; Qian, Xuyu; TCW, Julia; Kouznetsova, Jennifer; Ogden, Sarah C; Hammack, Christy; Jacob, Fadi; Nguyen, Ha Nam; Itkin, Misha; Hanna, Catherine; Shinn, Paul; Allen, Chase; Michael, Samuel G; Simeonov, Anton; Huang, Wenwei; Christian, Kimberly M; Goate, Alison; Brennand, Kristen J; Huang, Ruili; Xia, Menghang; Ming, Guo-li; Zheng, Wei; Song, Hongjun; Tang, Hengli (2016). "Identification of small-molecule inhibitors of Zika virus infection and induced neural cell death via a drug repurposing screen". Nature Medicine. 22: 1101–1107. doi:10.1038/nm.4184. ISSN 1078-8956. PMID 27571349.
  15. ^ Ren, X; Duan, L; He, Q; Zhang, Z; Zhou, Y; Wu, D; Pan, J; Pei, D; Ding, K (2010). "Identification of Niclosamide as a New Small-Molecule Inhibitor of the STAT3 Signaling Pathway". ACS Med Chem Lett. 1: 454–9. doi:10.1021/ml100146z. PMC 4007964. PMID 24900231.

Further reading[edit]

  • Taber, Clarence Wilbur; Venes, Donald; Thomas, Clayton L. (2001). Taber's cyclopedic medical dictionary. Philadelphia: F.A.Davis Co.

External links[edit]