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Flucytosine, a fluorinated pyrimidine analogue, is a synthetic antimycotic drug. Chemically it is referred to as 4-amino-5-fluoro-2(1H)-pyrimidinon. The sum formula is C4H4FN3O. Fucytosine has the CAS-Number 2022-85-7. It is structurally related to the cytostatic flourouracil and to floxuridine. It is available in oral and in some countries also in injectable form. A common brand name is AncobonĀ®. The drug is dispensed in capsules of 250 mg and 500 mg strength. The injectable form is diluted in 250ml NaCl-solution to contain 2.5 grams totally (10mg per ml). more...

Folic acid
Fusidic acid

The solution is physically incompatible with other drugs including Amphotericin B.


Mechanisms of action

Two major mechanisms of acton have been elucidated, one is that the drug is intrafungally converted into the cytostatic flourouracil that undergoes further steps of activation and finally interacts as 5-fluorouridinetriphosphate with RNA-biosynthesis and disturbs therefore the building of certain essential proteins. The other mechanism is the conversion into 5-flourodeoxyuridinemonophosphate which inhibits fungal DNA-synthesis.

Spectrum of susceptible fungi and Resistance

Flucytosine is as well in vitro and in vivo active against some strains of Candida and Cryptococcus. Limited studies demonstrate that Flucytosine may be of value against infections with Sporothrix, Aspergillus, Cladosporium, Exophila, and Phialophora. Resistance is quite commonly seen as well in treatment naive patients and under current treatment with Flucytosine. In different strains of Candida resistance has been noted to occur in 1 to 50% of all specimen obtained from patients.

Pharmacokinetic data

Flucytosine is well absorbed (75 to 90%) from the GI-Tract. Intake with meals slows the resorption, but does not decrease the amount resorbed. Following an oral dose of 2 grams peak serum levels are reached after approximately 6 hours. The time to peak level decreases with continued therapy. After 4 days peak levels are measured after 2 hours. The drug is eliminated renally. In normal patients Flucytosine has reportedly a half-life of 2.5 to 6 hours. In patients with impared renal function higher serum levels are seen and the drug tends to cumulate in these patients. The drug is mainly excreted unchanged in the urine (90% of an oral dose) and only traces are metabolized and excreted in the feces. Therapeutic serum levels range from 25 to 100mcg/ml. Serum levels in exceed of 100mcg are associated with a higher incidence of side-effects. Periodic measurements of serum levels are recommended for all patients and are a must in patients with renal damage.

Human overdose

Symptoms and their severities are unknown, because Flucytosine is used under close medical supervision, but expected to be an excess of the usually encountered side-effects on bone-marrow, GI-Tract, liver, and kidney-function. Vigouros hydration and hemodialysis may be helpful to remove the drug from the body. Hemodialysis is particular useful in patients with impaired renal function.

Human carcinogenity

It is not known, if Flucytosine is a human carcinogen. The issue has been raised because traces of 5-fluorouracil, which is a known carcinogen, are found in the colon resulting from the metabolization of Flucytosine.


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Abnormal vaginal discharge: what does and does not work in treating underlying causes
From Journal of Family Practice, 11/1/04 by Linda French

Practice recommendations

* Treat bacterial vaginosis with oral or intravaginal metronidazole or with clindamycin (SOR: A); recurrences are common (SOR: C).

* Oral and intravaginal imidazoles are equally effective in the treatment of candidiasis (SOR: A); alternate therapies for resistant cases have been little studied.

* Oral metronidazole is the standard therapy for trichomoniasis (SOR: A). Oral tinidazole, newly available in the US in 2004, should be used in resistant cases (SOR: B).

Antifungal medications for intravaginal use have been available in the United States for more than a decade. Women may be inclined to self-diagnose yeast infections with any vaginal discharge or other vulvovaginal symptoms that they deem abnormal. As we saw in the first part of this article, "Abnormal vaginal discharge: Using office diagnostic testing more effectively" (JFP 2004; 53[10]:805-814), abnormal discharge is more likely to be bacterial vaginosis or no pathogen at all. Potential delay in diagnosis and treatment of a sexually transmitted disease is also a concern. Increasing resistance of Candida sp. to imidazoles is associated with indiscriminate use of over-the-counter products.


The standard treatment for bacterial vaginosis (BV) has been oral metronidazole (Flagyl) 500 mg twice daily for 5 to 7 days. Intravaginal 0.75% metronidazole gel (MetroGel) has been shown to be as effective as oral metronidazole (SOR: A). (1,2)

Oral metronidazole can cause nausea and abdominal pain in some patients; vaginal treatment may be preferable for them. A meta-analysis of 52 studies of regimens of oral metronidazole at a dose of 2 g daily of varying duration showed similar initial cure rates of 85%, 87%, 86%, and 87% for 1, 2, 5, and 7 days, respectively (strength of recommendation [SOR]: A). (3) Single-dose therapy may improve adherence (SOR: C).

Clindamycin (Cleocin), orally or in vaginal cream, for 5 days is also effective for BV (SOR: A). (4-8) Clindamycin cream is used at a dose of 5 g daily and a concentration of 2%. Lower concentration (1%) has been less effective. (6) Oral regimens range from 300 mg twice daily to 450 mg 3 times daily. Oral and vaginal preparations have shown equal efficacy in direct comparisons (SOR: A). (8) A 3-day course of vaginal clindamycin is as effective as a 5-day course (SOR: B). (9)

Several studies have compared clindamycin and metronidazole head to head. They have shown similar cure rates that were not statistically different in the 75% to 90% range (SOR: A). (4,5,10,11)

Other antibiotics that have shown in vitro efficacy for treating the spectrum of microbes associated with BV are amoxicillin-clavulanate (Augmentin), imipenem (Primaxin), and cefmetazole (Zefazone) (SOR: C). (8,12) Some Mobiluncus strains show resistance to metronidazole (SOR: C). (12)

Recurrences of BV are common. The initial regimen or an alternative regimen may be used. A longer, 10- to 14-day, course of antibiotic therapy has been recommended by one expert for treating relapses (SOR: C). (13) Recolonizing the vagina with lactobacilli by eating yogurt or using bacteria-containing suppositories is an approach that deserves further study (SOR: C). (14) Suppressive therapy such as intravaginal metronidazole twice weekly may also be considered as maintenance therapy to prevent recurrences (SOR: C).

BV and pregnancy

A number of studies have been published on screening for BV in pregnancy using Gram stain and on treating positive cases with antibiotics. While studies that used metronidazole for treatment have not shown consistently good results, more recent studies using clindamycin orally or intravaginally have been promising (SOR: B). (7,15) Oral dosing at 300 mg twice daily, at 12 to 22 weeks gestation, has reduced preterm delivery for pregnant women with BV diagnosed by Nugent's criteria (number needed to treat [NNT]=10). (7) Likewise, for women with BV treated at 13 to 20 weeks gestation, intravaginal clindamycin therapy for 3 days has reduced the incidence of preterm births (NNT=17). (15)

Clindamycin appears to be the treatment of choice for BV in pregnancy (SOR: C) since it is considered safe (category B) throughout pregnancy, and because use of metronidazole in the first trimester is controversial.


Treating vulvovaginal candidiasis (VVC) with intravaginal imidazoles reduces symptoms with NNT=3 after 1 month (SOR: A) (Table). (16) No difference has been seen in outcomes with the various imidazoles or with treatment durations of 1 to 14 days. Intravaginal nystatin also decreases symptoms of VVC, with a NNT of 3 after 1 week compared with placebo (SOR: B).

Data showing that imidazoles are more effective than nystatin are not strong (SOR: B). A Clinical Evidence review (16) identified 1 trial comparing intravaginal miconazole, clotrimazole, econazole, and nystatin; symptomatic relapse was lower with intravaginal imidazoles than with nystatin. Another trial comparing clotrimazole and nystatin showed no difference in the proportion of women with persistent symptoms after 4 weeks. An open label study (17) comparing econazole, miconazole, and nystatin showed that the imidazoles had more antifungal activity, but there was no difference in clinical outcome assessment.

Oral treatments are popular, most commonly a single dose of fluconazole. Oral itraconazole and ketoconazole have also been used successfully (SOR: A). (18-21) A systematic review of oral vs vaginal azoles showed similar efficacy, but more side effects occurred with oral therapy (SOR: A). (22) Gastrointestinal side effects occur in up to 15% of women. (23)

Treating complicated WC

About 5% of women diagnosed with VVC will have frequent recurrences, 4 or more per year. (24) Current therapies are fungistatic rather than fungicidal, so the yeast are reduced but not eradicated. Hypersensitivity and allergic reactions to topical preparations may be confused with recurrences. Experts recommend that, if wet mount or culture results confirm recurrent vaginitis, topical therapy should be increased from 5 to 7 days up to 10 to 14 days, or that a second oral fluconazole tablet be given 3 days after the first (SOR: C). (24) Women with severe cases of VVC also benefit from 2 sequential doses of fluconazole given 3 days apart (SOR: B). (25)

Suppressive therapy may be used after initial treatment for 6 months or more (SOR: B). Suppressive therapy options include oral fluconazole 150 mg or vaginal clotrimazole 500 mg once a week, oral or intravaginal nystatin twice weekly, and oral itraconazole 200 mg monthly. (24,26)

Non-albicans species tend to be more resistant to oral and topical azoles (SOR: B). (27-29) If this species is detected on culture, a long course of suppressive therapy should be attempted (SOR: C). (24) If imidazole therapy fails to control symptoms, suspect resistance.

Resistance to azoles may be demonstrated by in vitro susceptibility testing. Cross-resistance to topical and oral (fluconazole) azoles has been documented. (30) There have been few studies of alternatives to azoles for treatment of resistant yeast vaginitis. One little-studied alternative is intravaginal boric acid, which may be used as a 14-day course of 600 mg dally in gelatin capsules (SOR: C). (31) Nystatin and flucytosine (Ancoban) for 7 to 14 days are other alternatives (SOR: C). (24)

Candida in pregnancy

Commonly used topical imidazoles are classified as category C in pregnancy and have not been associated with increased risk of birth defects.


Current treatment for trichomoniasis is oral metronidazole, given as a 2-g single dose, 250 mg 3 times daily for 7 days or 500 mg twice a day for 7 days. Treatment should also be given to the woman's partner (SOR: A). (32) Intravaginal therapy is not effective, probably due to the parasite's presence in inaccessible areas such as the vaginal glands and urethra. (33,34) Short-term treatment is comparable with long-term treatment, with similar rates of nausea and vomiting (SOR: A). (32) A 1.5-g single-dose treatment has been shown to be equivalent to 2 g (SOR: B). (35)

The incidence metronidazole-resistant trichomoniasis has been estimated at 5%. (36) In such cases, higher-dose therapy may be still be effective. For low to moderate resistance, 2 too 2.5 g daily for 3 to 10 days has been recommended (SOR: B). (37) Intravenous high-dose metronidazole, 2 g every 8 hours for 3 days, has been reported to successfully treat highly resistant trichomonas (SOR: C). (38) Another case report of 2 women with presumed allergy to metronidazole were successfully treated with incremental dosing of IV metronidazole (SOR: C). (39) A small case series of women with metronidazole allergy or resistance treated with paromomycin cream intravaginally showed cure in 6 of 9 cases (SOR: C). (40) Oral tinidazole has been approved in 2004 for use in the treatment of metronidazole-resistant trichomoniasis (SOR: B). (41)


(1.) Hillier SL, Lipinski C, Briselden AM, Eschenbach DA. Efficacy of intravaginal 0.75% metronidazole gel for the treatment of bacterial vaginosis. Obstet Gynecol 1993; 81:963-967.

(2.) Hanson IM, McGregor JA, Hillier SL, et al. Metronidazole for bacterial vaginosis. A comparison of vaginal gel vs. oral therapy. J Reprod Med 2000; 45:889-896.

(3.) Lugo-Miro VI, Green M, Mazur L. Comparison of different metronidazole therapeutic regimens for bacterial vaginosis. A meta-analysis. JAMA 1992; 268:92-95.

(4.) Ferris DG, Litaker MS, Woodward L, Mathis D, Hendrich J. Treatment of bacterial vaginosis: a comparison of oral metronidazole, metronidazole vaginal gel, and clindamycin vaginal cream. J Fam Pract 1995; 41:443-449.

(5.) Fischbach F, Petersen EE, Weissenbacher ER, Martius J, Hosmann J, Mayer H. Efficacy of clindamycin vaginal cream versus oral metronidazole in the treatment of bacterial vaginosis. Obstet Gynecol 1993; 82:405-410.

(6.) Hillier S, Krohn MA, Watts DH, Wolner-Hanssen P, Eschenbach D. Microbiologic efficacy of intravaginal clindamycin cream for the treatment of bacterial vaginosis. Obstet Gynecol 1990; 76:407-413.

(7.) Ugwumadu A, Manyonda I, Reid F, Hay P. Effect of early oral clindamycin on late miscarriage and preterm delivery in asymptomatic women with abnormal vaginal flora and bacterial vaginosis: a randomised controlled trial. Lancet 2003; 361:983-988.

(8.) Mikamo H, Kawazoe K, Izumi K, Watanabe K, Ueno K, Tamaya T. Comparative study on vaginal or oral treatment of bacterial vaginosis. Chemotherapy 1997; 43:60-68.

(9.) Ahmed-Jushuf IH, Shahmanesh M, Arya OR The treatment of bacterial vaginosis with a 3 day course of 2% clindamycin cream: results of a multicentre, double blind, placebo controlled trial. B V Investigators Group. Genitourin Med 1995; 71:254-256.

(10.) Schmitt C, Sobel JD, Meriwether C. Bacterial vaginosis: treatment with clindamycin cream versus oral metronidazole. Obstet Gynecol 1992; 79:1020-1023.

(11.) Paavonen J, Mangioni C, Martin MA, Wajszczuk CR Vaginal clindamycin and oral metronidazole for bacterial vaginosis: a randomized trial. Obstet Gynecol 2000; 96:256-260.

(12.) Puapermpoonsiri S, Watanabe K, Kato N, Ueno K. In vitro activities of 10 antimicrobial agents against bacterial vaginosis-associated anaerobic isolates from pregnant Japanese and Thai women. Antirnicrob Agents Chernother 1997; 41:2297-2299.

(13.) Sobel JD. Vaginitis. N Engl J Med 1997; 337:1896-1903.

(14.) Shalev E, Battino S, Weiner E, Colodner R, Keness Y. Ingestion of yogurt containing Lactobacillus acidophilus compared with pasteurized yogurt as prophylaxis for recurrent candidal vaginitis and bacterial vaginosis. Arch Faro Med 1996; 5:593-596.

(15.) Lamont RF, Jones BM, Mandal D, Hay PE, Sheehan M. The efficacy of vaginal clindamycin for the treatment of abnormal genital tract flora in pregnancy. Infect Dis Obstet Gynecol 2003; 11:181-189.

(16.) Marrazzo J. Vulvovaginal candidiasis. BMJ 2002; 325:586.

(17.) Emele FE, Fadahunsi AA, Anyiwo CE, 0gunleye O. A comparative clinical evaluation of econazole nitrate, miconazole, and nystatin in the treatment of vaginal candidiasis. West Afr J Med 2000; 19:12-15.

(18.) Stein GE, Mummaw N. Placebo-controlled trial of itraconazole for treatment of acute vaginal candidiasis. Antirnicrob Agents Chemother 1993; 37:89-92.

(19.) Van der Pas H, Peeters F, Janssens D, Snauwaert E, Van Cutsem J. Treatment of vaginal candidosis with oral ketoconazole. Eur J Obstet Gynecol Reprod Biol 1983; 14:399-404.

(20.) Sanz Sanz F, del Palacio Hernanz A. Randomized comparative trial of three regimens of itraconazole for treatment of vaginal mycoses. Rev Infect Dis 1987; 9 Suppl 1:S139-S142.

(21.) Silva-Cruz A, Andrade L, Sobral L, Francisca A. Itraconazole versus placebo in the management of vaginal candidiasis. Int J Gynaecol Obstet 1991; 36:229-232.

(22.) Watson MC, Grimshaw JM, Bond CM, Mollison J, Ludbrook A. Oral versus intra-vaginal imidazole and triazole anti-fungal agents for the treatment of uncomplicated vulvovaginal candidiasis (thrush): a systematic review. BJOG 2002; 109:85-95.

(23.) van Heusden AM, Merkus HM, Corbeij RS, et al. Single-dose oral fluconazole versus single-dose topical miconazole for the treatment of acute vulvovaginal candidosis. Acta Obstet Gynecol Scand 1990; 69:417-422.

(24.) Sobel JD. Vulvovaginitis. When Candida becomes a problem. Dermatol Clin 1998; 16:763-768, xii.

(25.) Sobel JD, Kapernick PS, Zervos M, et al. Treatment of complicated Candida vaginitis: comparison of single and sequential doses of fluconazole. Am J Obstet Gynecol 2001; 185:363-369.

(26.) Creatsas GC, Charalambidis VM, Zagotzidou EH, Anthopoulou HN, Michailidis DC, Aravantinos DI. Chronic or recurrent vaginal candidosis: short-term treatment and prophylaxis with itraconazole. Clin Ther 1993; 15:662-671.

(27.) Horowitz BJ, Giaquinta D, Ito S. Evolving pathogens in vulvovaginal candidiasis: implications for patient care. J Clin Pharmacol 1992; 32:248-255.

(28.) del Palacio A, Sanz F, Sanchez-Alor G, et al. Double-blind randomized dose-finding study in acute vulvovaginal candidosis. Comparison of flutrimazole site-release cream (1, 2 and 4%) with placebo site-release vaginal cream. Mycoses 2000; 43:355-365.

(29.) Singh S, Sobel JD, Bhargava P, Boikov D, Vazquez JA. Vaginitis due to Candida krusei: epidemiology, clinical aspects, and therapy. Clin Infect Dis 2002; 35:1066-1070.

(30.) Cross EW, Park S, Perlin DS. Cross-Resistance of clinical isolates of Candida albicans and Candida glabrata to over-the-counter azoles used in the treatment of vaginitis. Microb Drug Resist 2000; 6:155-161.

(31.) Sobel JD, Chaim W. Treatment of Torulopsis glabrata vaginitis: retrospective review of boric acid therapy. Clin Infect Dis 1997; 24:649-652.

(32.) Forna F, Gulmezoglu AM. Interventions for treating trichomoniasis in women. Cochrane Database Syst Rev 2003 (2):CD000218.

(33.) duBouchet L, McGregor JA, Ismail M, McCormack WM. A pilot study of metronidazole vaginal gel versus oral metronidazole for the treatment of Trichomonas vaginalis vaginitis. Sex Transrn Dis 1998; 25:176-179.

(34.) Tidwell BH, Lushbaugh WB, Laughlin MD, Cleary JD, Finley RW. A double-blind placebo-controlled trial of single-dose intravaginal versus single-dose oral metronidazole in the treatment of trichomonal vaginitis. J Infect Dis 1994; 170:242-246.

(35.) Spence MR, Harwell TS, Davies MC, Smith JL. The minimum single oral metronidazole dose for treating trichomoniasis: a randomized, blinded study. Obstet Gynecol 1997; 89:699-703.

(36.) Petrin D, Delgaty K, Bhatt R, Garber G. Clinical and microbiological aspects of Trichomonas vaginalis. Clin Microbiol Rev 1998; 11:300-317.

(37.) Lossick JG, Kent HL. Trichomoniasis: trends in diagnosis and management. Am J Obstet Gynecol 1991; 165:1217-1222.

(38.) Dombrowski MP, Sokol RJ, Brown WJ, Bronsteen RA. Intravenous therapy of metronidazole-resistant Trichomonas vaginalis. Obstet Gynecol 1987; 69:524-525.

(39.) Pearlman MD, Yashar C, Ernst S, Solomon W. An incremental dosing protocol for women with severe vaginal trichomoniasis and adverse reaction to metronidazole. Am J Obstet Gynecol 1996; 174:934-936.

(40.) Nyirjesy P, Sobel JD, Weitz MV, Leaman DJ, Gelone SP. Difficult-to-treat trichomoniasis: results with paromomycin cream. Clin Infect Dis 1998; 26:986-988.

(41.) Sobel JD, Nyirjesy P, Brown W. Tinidazole therapy for metronidazole-resistant vaginal trichomoniasis. Clin Infect Dis 2001; 33:1341-1346.

Linda French, MD Michigan State University, East Lansing, Mich

Jennifer Horton, DO Genesys Regional Medical Center Family Practice Residency, Grand Blanc, Mich

Michelle Matousek, DO Henry Ford Health System, Detroit, Mich

Corresponding author: Linda French, MD, Associate Professor, Department of Family Practice, College of Human Medicine, Michigan State University, B101 Clinical Center, East Lansing, MI 48824. E-mail:

COPYRIGHT 2004 Dowden Health Media, Inc.
COPYRIGHT 2004 Gale Group

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