Antifungal
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Antifungal drug

An antifungal drug is a medication used to treat fungal infections such as athlete's foot, ringworm, candidiasis (thrush), serious systemic infections such as cryptococcal meningitis, and others. Such drugs are usually obtained by a doctor's prescription or purchased over-the-counter.

Mode of action

Antifungals work by exploiting differences between mammalian and fungal cells to kill the fungal organism without dangerous effects on the host. Unlike bacteria, both fungi and humans are eukaryotes. Thus fungal and human cells are similar at the molecular level. This makes it more difficult to find or design drugs that target fungi without affecting human cells. Consequently, many antifungal drugs cause side-effects. Some of these side-effects can be life-threatening if the drugs are not used properly.

Precaution

Apart from side-effects like liver-damage or affecting estrogen levels , many medicines can cause allergic reactions in people. For example, the azole group of drugs is known to have caused anaphylaxis.

There are also many drug interactions. Patients must read in details the enclosed data sheet(s) of the medicine. For example, the azole antifungals such as ketoconazole or itraconazole can be both substrates and inhibitors of the P-glycoprotein, which (among other functions) excretes toxins and drugs into the intestines.[1] Azole antifungals also are both substrates and inhibitors the cytochrome P450 family CYP3A4,[1] causing increased concentration when administering, for example, calcium channel blockers, immunosuppressants, chemotherapeutic drugs, benzodiazepines, tricyclic antidepressants, macrolides and SSRIs.

Classes

Polyene antifungals

Main article: Polyene antimycotic

A polyene is a molecule with multiple conjugated double bonds. A polyene antifungal is a macrocyclic polyene with a heavily hydroxylated region on the ring opposite the conjugated system. This makes polyene antifungals amphiphilic. The polyene antimycotics bind with sterols in the fungal cell membrane, principally ergosterol. This changes the transition temperature (Tg) of the cell membrane, thereby placing the membrane in a less fluid, more crystalline state. As a result, the cell's contents leak and the cell dies. Animal cells contain cholesterol instead of ergosterol and so they are much less susceptible. As a polyene's hydrophobic chain is shortened, its sterol binding activity is increased. Therefore, further reduction of the hydrophobic chain may result in it binding to cholesterol, making it toxic to animals.

Imidazole, triazole, and thiazole antifungals

The imidazole and triazole drugs are synthetic antifungal drugs that inhibit the enzyme cytochrome P450 14α-demethylase. This enzyme converts lanosterol to ergosterol, and is required in fungal cell membrane synthesis. These drugs also block steroid synthesis in humans.

[edit] Imidazoles

The triazoles are newer, less toxic[citation needed] and more effective[citation needed]:

Triazoles

Thiazoles

Allylamines

Allylamines inhibit squalene epoxidase, another enzyme required for ergosterol synthesis:

  • Terbinafine – marketed as "Lamisil" in North America, Australia, the UK, Germany and the Netherlands
  • Amorolfine
  • Naftifine – marketed as "Naftin" in North America
  • Butenafine – marketed as Lotrimin Ultra

Echinocandins

Echinocandins inhibit the synthesis of glucan in the cell wall, probably via the enzyme 1,3-β glucan synthase:

Others

  • Haloprogin – discontinued due to the emergence of more modern antifungals with fewer side effects [4]
  • Sodium bicarbonate (NaHCO3) [5][6] – shown effective against green mold on citrus under refrigeration and powdery mildew on rose plants

Alternatives[7]

Anti-dandruff shampoos

Antifungal drugs (such as ketoconazole) are often found in anti-dandruff shampoos. The antifungal drugs inhibit the yeast Malassezia globosa which encourages seborrhoeic dermatitis and tinea versicolor.

Active ingredient Example of product Comments
Ketoconazole[8] Nizoral, or Fungoral There is a claim that Nizoral shampoo has hair loss benefits but Nizoral Shampoo does not have FDA approval as a hair loss remedy.[9]
Ciclopirox olamine Loprox Has similar efficacy to ketoconazole with a relative increase in subjective symptom relief due to its inherent anti-inflammatory properties[10].
Piroctone olamine (Octopirox)[11] Nivea Complete Control[12] A replacement for the commonly used compound zinc pyrithione.
Zinc pyrithione[13] Head & Shoulders, Johnson and Johnson ZP-11, Clinic All Clear, Pantene Pro V, Sikkai Powder An antifungal and antibacterial agent first reported in the 1930s.
Selenium sulfide Selsun Blue, Vichy Dercos Anti-Dandruff shampoo, other varieties of Head & Shoulders In the United States, 1% strength is available over-the-counter, and a 2.5% strength is also available with a prescription.
Tar[14] Neutrogena T-Gel  
Tea tree oil[15] Dr. Bronner's Castile Soap    

See also

References

  1. ^ a b doctorfungus > Antifungal Drug Interactions Content Director: Russell E. Lewis, Pharm.D. Retrieved on Jan 23, 2010
  2. ^ Wilson, Gisvold, Block, Beale (2004). Wilson and Gisvold's Textbook of Organic Medicinal and Pharmaceutical Chemistry. Philadelphia, Pa.: Lippincott Williams & Wilkins. ISBN 0781734819.  http://books.google.com/books?id=CIpWhgWV5q0C&pg=RA1-PA234&lpg=RA1-PA234&dq=%22benzoic+acid%22+antifungal+tinea&source=web&ots=nK8OrzL8p3&sig=AIzhJBiDYl1-sffvCRmynMan06Q
  3. ^ "antifung". http://faculty.swosu.edu/scott.long/phcl/antifung.htm. Retrieved 2008-07-09. 
  4. ^ "Haloprogin". DrugBank. University of Alberta. November 6, 2006. http://redpoll.pharmacy.ualberta.ca/drugbank/cgi-bin/getCard.cgi?CARD=APRD01011.txt. Retrieved 2007-02-17. 
  5. ^ Evaluation of antifungal activity of ... bicarbonate salts ... in control of citrus green mold, by Zamani M, Sharifi Tehrani A, Ali Abadi AA., Department of Plant Protection, University of Tehran, Iran
  6. ^ Use of Baking Soda as a Fungicide on Plants, By George Kuepper, Raeven Thomas, and Richard Earles, © NCAT November 2001
  7. ^ Pattnaik S, Subramanyam VR, Kole C (1996). "Antibacterial and antifungal activity of ten essential oils in vitro". Microbios 86 (349): 237–46. PMID 8893526. http://cat.inist.fr/?aModele=afficheN&cpsidt=3245986. 
  8. ^ McGrath J, Murphy GM (1991). "The control of seborrhoeic dermatitis and dandruff by antipityrosporal drugs". Drugs 41 (2): 178–84. doi:10.2165/00003495-199141020-00003. PMID 1709848. 
  9. ^ Nizoral Shampoo as a Hair Loss Remedy? http://www.dermadoctor.com/pages/newsletter198.asp
  10. ^ Ratnavel RC, Squire RA, Boorman GC (2007). "Clinical efficacies of shampoos containing ciclopirox olamine (1.5%) and ketoconazole (2.0%) in the treatment of seborrhoeic dermatitis". J Dermatolog Treat 18 (2): 88–96. doi:10.1080/16537150601092944. PMID 17520465. 
  11. ^ Dubini F, Bellotti MG, Frangi A, Monti D, Saccomani L (2005). "In vitro antimycotic activity and nail permeation models of a piroctone olamine (octopirox) containing transungual water soluble technology". Arzneimittel-Forschung 55 (8): 478–83. PMID 16149717. 
  12. ^ http://products2.nivea.com/products.php?page_id=1298&lan=com
  13. ^ Warner RR, Schwartz JR, Boissy Y, Dawson TL (2001). "Dandruff has an altered stratum corneum ultrastructure that is improved with zinc pyrithione shampoo". J. Am. Acad. Dermatol. 45 (6): 897–903. doi:10.1067/mjd.2001.117849. PMID 11712036. 
  14. ^ Piérard-Franchimont C, Piérard GE, Vroome V, Lin GC, Appa Y (2000). "Comparative anti-dandruff efficacy between a tar and a non-tar shampoo". Dermatology (Basel) 200 (2): 181–4. doi:10.1159/000018362. PMID 10773717. 
  15. ^ Prensner R (2003). "Does 5% tea tree oil shampoo reduce dandruff?". The Journal of family practice 52 (4): 285–6. PMID 12681088. http://www.jfponline.com/Pages.asp?AID=1437. 

External links

  • Antifungal Drugs - Detailed information on antifungals from the Fungal Guide written by Drs. R. Thomas and K. Barber
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