Difference between revisions of "Halofantrine"

Latest revision as of 10:26, 20 September 2010

Halofantrine is a drug used to treat malaria. Halofantrine's structure contains a substituted phenanthrene, and is related to the antimalarial drugs quinine and lumefantrine. Marketed as Halfan, halofantrine is never used to prevent malaria and its mode of action is unknown. A crystallographic study have shown that halofantrine binds to hematin in vitro, suggesting a possible mechanism of action ^[1]. Alternatively or in addition, halofantrine has been shown to bind to plasmpesin, a haemoglobin degrading enzyme unique to the malarial parasites ^[2].

Adverse reactions

Halofantrine can cause abdominal pain, diarrhoea, vomiting, rash, headache, itching and elevated liver enzymes.

It can be associated with cardiotoxicity.^[3] The most dangerous side effect is cardiac arrhythmias: halofantrine causes significant QT prolongation,^[4] and this effect is seen even at standard doses. The drug should therefore not be given to patients with cardiac conduction defects and should not be combined with mefloquine. A survey from 2009 suggests that the drug is safe when correctly administered ^[5]

Pharmacology

The mechanism of action of halofantrine is unknown. The absorption of halofantrine is erratic, but is increased when taken with fatty food. Because of fears of toxicity due to increased halofantrine blood levels, halofantrine should be taken on an empty stomach.

Plasma levels peak at 16 hours and the half-life of the drug is about 4 days.

Uses

Halofantrine is only used to treat malaria. It is not used to prevent malaria (prophylaxis) because of the risk of toxicity and unreliable absorption.

Dosing

• Adult dose: Three doses of 500 mg six hours apart.

Halofantrine should be taken on an empty stomach.

Manufacturing information and availability

• Halfan (GlaxoSmithKline) is available as 250 mg tablets. A full treatment cost (6 tablets) costs US$1.40 in the developing world. Halofantrine is not available in the UK or U.S.

References

1. ↑ de Villiers KA, Marques HM, Egan TJ (2008). "The crystal structure of halofantrine-ferriprotoporphyrin IX and the mechanism of action of arylmethanol antimalarials". J. Inorg. Chem. 102 (8): 1660–7. doi:10.1016/j.jinorgbio.2008.04.001. PMID 18508124. CS1 maint: Multiple names: authors list (link)
2. ↑ Friedman R, Caflisch A (2009). "Discovery of plasmepsin inhibitors by fragment-based docking and consensus scoring". ChemMedChem. 4 (8): 1317–26. doi:10.1002/cmdc.200900078. PMID 19472268. 
3. ↑ Lua error in package.lua at line 80: module 'Module:Citation/CS1/Suggestions' not found.
4. ↑ Sánchez-Chapula JA, Navarro-Polanco RA, Sanguinetti MC (2004). "Block of wild-type and inactivation-deficient human ether-a-go-go-related gene K+ channels by halofantrine". Naunyn Schmiedebergs Arch. Pharmacol. 370 (6): 484–91. doi:10.1007/s00210-004-0995-5. PMID 15558243. CS1 maint: Multiple names: authors list (link)
5. ↑ Bouchaud O, Imbert P, Touze JE, Dodoo AN, Danis M, Legros F (2009). "Fatal cardiotoxicity related to halofantrine: a review based on a worldwide safety data base". Malaria J. 8: 289. doi:10.1186/1475-2875-8-289. PMC 2801676 Freely accessible. PMID 20003315. CS1 maint: Multiple names: authors list (link)