|Systematic (IUPAC) name|
|Pregnancy cat.||D (Au), C (U.S.)|
|Legal status||S3/S4 (Au), POM (UK), ℞-only (U.S.)|
|Routes||Oral, IV, topical|
|Half-life||30 hours (range 20-50 hours)|
|ATC code||D01 J02|
|Mol. mass||306.271 g/mol|
|(what is this?)|
Fluconazole // is a triazole antifungal drug used in the treatment and prevention of superficial and systemic fungal infections. In a bulk powder form, it appears as a white crystalline powder, and it is very slightly soluble in water and soluble in alcohol. It is commonly marketed under the trade names Diflucan and Trican (Pfizer).
Mechanism of action
Like other imidazole- and triazole-class antifungals, fluconazole inhibits the fungal cytochrome P450 enzyme 14α-demethylase. Mammalian demethylase activity is much less sensitive to fluconazole than fungal demethylase. This inhibition prevents the conversion of lanosterol to ergosterol, an essential component of the fungal cytoplasmic membrane, and subsequent accumulation of 14α-methyl sterols. Fluconazole is primarily fungistatic; however, it may be fungicidal against certain organisms in a dose-dependent manner, specifically Cryptococcus.
It is interesting to note, when fluconazole was in development at Pfizer, it was decided early in the process to avoid producing any chiral centers in the drug so subsequent synthesis and purification would not encounter difficulties with enantiomer separation and associated variations in biological effect. A number of related compounds were found to be extremely potent teratogens, and were subsequently discarded.
Fluconazole is active against:
- Blastomyces dermatitidis
- Candida spp. (except C. krusei and C. glabrata)
- Coccidioides immitis
- Cryptococcus neoformans
- Epidermophyton spp.
- Histoplasma capsulatum
- Microsporum spp.
- Trichophyton spp.
Fungal resistance to drugs in the azole class tends to occur gradually over the course of prolonged drug therapy, resulting in clinical failure in immunocompromised patients (e.g., patients with advanced HIV receiving treatment for thrush or esophageal Candida infection).
In C. albicans, resistance occurs by way of mutations in the ERG11 gene, which codes for 14α-demethylase. These mutations prevent the azole drug from binding, while still allowing binding of the enzyme's natural substrate, lanosterol. Development of resistance to one azole in this way will confer resistance to all drugs in the class. Another resistance mechanism employed by both C. albicans and C. glabrata is increasing the rate of efflux of the azole drug from the cell, by both ATP-binding cassette and major facilitator superfamily transporters. Other gene mutations are also known to contribute to development of resistance.
The full spectrum of fungal susceptibility and resistance to fluconazole can be found in the TOKU-E's product data sheet.
Following oral dosing, fluconazole is almost completely absorbed within two hours. Bioavailability is not significantly affected by the absence of stomach acid. Concentrations measured in the urine, tears, and skin are approximately 10 times the plasma concentration, whereas saliva, sputum, and vaginal fluid concentrations are approximately equal to the plasma concentration, following a standard dose range of between 100 mg and 400 mg per day. The elimination half-life of fluconazole follows zero order kinetics, and only 10% of elimination is due to metabolism, the remainder being excreted in urine and sweat. Patients with impaired renal function will be at risk of overdose.
- Candidiasis caused by susceptible strains of Candida
- Tinea corporis, tinea cruris or tinea pedis
- Cryptococcal meningitis
Fluconazole can be used first-line for the following indications:
- Prophylaxis of candidiasis in immunocompromised people
- Auto-brewery syndrome
Dosage varies with indication and between patient groups, ranging from a two-week course of 150 mg/day for vulvovaginal candidiasis to 150–300 mg once weekly for resistant skin infections or some prophylactic indications. A dosage of 500–600 mg/day may be used for systemic or severe infections, and, in urgent infections such as meningitis caused by yeast, 800 mg/day have been used. Pediatric doses are measured at 6–12 mg/kg/d. A loading dose will be indicated when entering a daily dosage schedule; for example, a loading dose of 200 mg on the first day is commonly used with 150 mg/day following that.
Fluconazole is contraindicated in patients who:
- Have known hypersensitivity to other azole medicines such as ketoconazole
- Are taking terfenadine, if 400 mg per day multidose of fluconazole is administered
- Concomitant administration of fluconazole and quinidine, especially when fluconazole is administered in high dosages
- Take SSRIs such as Prozac or Zoloft
Fluconazole is secreted in human milk at concentrations similar to plasma. Therefore, the use of fluconazole in lactating mothers is not recommended.
Fluconazole therapy has been associated with QT interval prolongation, which may lead to serious cardiac arrhythmias. Thus, it is used with caution in patients with risk factors for prolonged QT interval, such as electrolyte imbalance or use of other drugs that may prolong the QT interval (particularly cisapride and pimozide).
Fluconazole has also rarely been associated with severe or lethal hepatotoxicity, so liver function tests are usually performed regularly during prolonged fluconazole therapy. In addition, it is used with caution in patients with pre-existing liver disease.
Some people are allergic to azoles, so those allergic to other azole drugs might be allergic to fluconazole. That is, some azole drugs have adverse side-effects. Some azole drugs may disrupt estrogen production in pregnancy, affecting pregnancy outcome. 
Fluconazole taken at a dose of 150 mg is in FDA pregnancy category C. However, high doses (400 mg to 800 mg a day) have been associated with a rare and distinct set of birth defects in infants. If taken at these doses, the pregnancy category is changed from category C to category D. Pregnancy category D means there is positive evidence of human fetal risk based on human data. In some cases, the potential benefits from use of the drug in pregnant women with serious or life-threatening conditions may be acceptable despite its risks. Fluconazole should not be taken during pregnancy or if one could become pregnant during treatment without first consulting a doctor. Oral fluconazole is not associated with a significantly increased risk of birth defects overall, although it does increase the odds ratio of tetralogy of Fallot, but the absolute risk is still low.
Fluconazole should not be taken with cisapride (Propulsid) due to the possibility of serious, even fatal, heart problems.[medical citation needed] In rare cases, severe allergic reactions including anaphylaxis may occur.[medical citation needed]
- Common (≥1% of patients): rash, headache, dizziness, nausea, vomiting, abdominal pain, diarrhea, and/or elevated liver enzymes
- Infrequent (0.1–1% of patients): anorexia, fatigue, constipation
- Rare (<0.1% of patients): oliguria, hypokalaemia, paraesthesia, seizures, alopecia, Stevens–Johnson syndrome, thrombocytopenia, other blood dyscrasias, serious hepatotoxicity including hepatic failure, anaphylactic/anaphylactoid reactions
- Very rare: prolonged QT interval, torsades de pointes
- FDA is now saying treatment with chronic, high doses (400–800 mg/day) of fluconazole during the first trimester of pregnancy may be associated with a rare and distinct set of birth defects in infants.
Fluconazole is an inhibitor of the human cytochrome P450 system, particularly the isozyme CYP2C9 (CYP3A4 to lesser extent). In theory, therefore, fluconazole decreases the metabolism and increases the concentration of any drug metabolised by these enzymes. In addition, its potential effect on QT interval increases the risk of cardiac arrhythmia if used concurrently with other drugs that prolong the QT interval. Berberine has been shown to exert synergistic effects with fluconazole even in drug-resistant Candida albicans infections.
Fluconazole is sold as a single 150 mg dose over the counter in Canada under the brand names Monicure and Canesten. In Mexico, it is sold over the counter as Alfumet, Afungil or Dofil. It is marketed under the brand name Candivast in the Persian Gulf area. In Colombia, it is marketed as Batén by Laboratorios Bussié. In Panama, it is marketed under the name Ibarin from different manufacturers. In Egypt, it is marketed under the names Diflucan, Flucoral, Fungican, Triconal. The No.1 brand in India is Zocon, available as Tablets, Lotion, Dusting Powder, Transgel and Eye Drop.
- MP Biomedicals
- Pfizer Australia Pty Ltd. Diflucan (Australian Approved Product Information). West Ryde (NSW): Pfizer Australia; 2004.
- Longley, Nicky; Muzoora, Conrad; Taseera, Kabanda; Mwesigye, James; Rwebembera, Joselyne; Chakera, Ali; Wall, Emma; Andia, Irene; Jaffar, Shabbar; Harrison, Thomas S. (2008). "Dose Response Effect of High‐Dose Fluconazole for HIV‐Associated Cryptococcal Meningitis in Southwestern Uganda". Clinical Infectious Diseases 47 (12): 1556–1561. doi:10.1086/593194. ISSN 1058-4838. PMID 18990067.
- Sweetman S, editor. Martindale: The complete drug reference. 34th ed. London: Pharmaceutical Press; 2004. ISBN 0-85369-550-4
- Bennett J.E. (2011). Chapter 57. Antifungal Agents. In L.L. Brunton, B.A. Chabner, B.C. Knollmann (Eds), Goodman & Gilman's The Pharmacological Basis of Therapeutics, 12e. Retrieved May 22, 2012 from http://www.accessmedicine.com.ezp1.lib.umn.edu/content.aspx?aID=16678770.
- Spectrum of fungal susptibility and resistance to fluconazole
- Rossi S, editor. Australian Medicines Handbook 2006. Adelaide: Australian Medicines Handbook; 2006. ISBN 0-9757919-2-3
- Product information from Pfizer Inc
- Kragie, Laura; Turner, Stephanie D.; Patten, Christopher J.; Crespi, Charles L.; Stresser, David M. (2002). "Assessing Pregnancy Risks of Azole Antifungals Using a High Throughput Aromatase Inhibition Assay". Endocrine Research 28 (3): 129–40. doi:10.1081/ERC-120015045. PMID 12489563.
- Fluconazole, PubMed Health
- Mølgaard-Nielsen, D.; Pasternak, B. R.; Hviid, A. (2013). "Use of Oral Fluconazole during Pregnancy and the Risk of Birth Defects". New England Journal of Medicine 369 (9): 830–839. doi:10.1056/NEJMoa1301066. PMID 23984730.
- Xu, Yi; Wang, Yan; Yan, Lan; Liang, Rong-Mei; Dai, Bao-Di; Tang, Ren-Jie; Gao, Ping-Hui; Jiang, Yuan-Ying (2009). "Proteomic Analysis Reveals a Synergistic Mechanism of Fluconazole and Berberine against Fluconazole-ResistantCandida albicans: Endogenous ROS Augmentation". Journal of Proteome Research 8 (11): 5296–5304. doi:10.1021/pr9005074. ISSN 1535-3893. PMID 19754040. Free Full Text
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- Insight Pharmaceuticals. Our Products: Monicure. N.p.: Insight Pharmaceuticals, n.d.Monistat. Insight Pharmaceuticals, 2013. Web. 24 July 2013. <http://www.monistat.ca/monicure>.