Fluconazole

What it is

Fluconazole is a small synthetic molecule, the first of a subclass of triazole antifungal drugs, supplied as tablets, an oral suspension and an intravenous solution. The label describes it as a white crystalline solid, slightly soluble in water and saline. It is not derived from a food or a plant extract. Because it is absorbed almost completely by mouth and penetrates widely in the body, including the cerebrospinal fluid, it is used for infections ranging from vaginal thrush to cryptococcal meningitis.

What the research says

Fluconazole treats infections caused by yeasts, mainly Candida and Cryptococcus. For uncomplicated vaginal thrush a single 150 mg dose is at least as good as a week of topical treatment, and a 2025 network meta-analysis of 50 trials found it marginally ahead on early cure. Taken weekly it keeps recurrent thrush away while it is being taken, with 90.8% of women disease-free at six months versus 35.9% on placebo, but only 42.9% versus 21.9% at twelve months once treatment stops. For serious infections it is often the weaker option: in invasive candidiasis anidulafungin succeeded in 75.6% of patients against 60.2% for fluconazole, and in cryptococcal meningitis flucytosine beat fluconazole as the partner drug for amphotericin B (31.1% versus 45.0% deaths at ten weeks). Its harms are mostly mild, but it carries a specific pregnancy signal and rare, sometimes fatal, liver injury, and Candida auris is resistant to it in 87-100% of isolates.

Evidence grade: Well established.

How it works

Drug class: Triazole antifungal; selective inhibitor of the fungal cytochrome P450 enzyme lanosterol 14-alpha-demethylase (CYP51)

Fungi need a fat called ergosterol to build their cell membranes. Fluconazole blocks the fungal enzyme that makes it, lanosterol 14-alpha-demethylase, so abnormal sterols pile up and the fungus stops growing rather than being killed outright. The label notes the equivalent human enzyme is far less sensitive, which is why the drug is reasonably well tolerated. Absorption is over 90% by mouth, food makes no difference, and the half-life is about 30 hours, so one dose can cover a simple yeast infection. (Source 1)

What it is used for

• A single 150 mg dose cures most uncomplicated episodes and was marginally better than multiple-day topical treatment for early clinical cure in a 50-trial network meta-analysis, though by the later follow-up oral and topical treatment were equivalent. The label's own US trials gave a 55% therapeutic cure rate, identical to intravaginal comparators. Evidence: established. (Source 2)
• The labelled indication is vaginal candidiasis, not a six-month weekly suppression regimen, so this use is off-label. A 387-woman placebo-controlled trial showed it works while taken (90.8% versus 35.9% disease-free at six months) but that most of the benefit is lost after stopping (42.9% versus 21.9% at twelve months). Evidence: established. (Source 3)
• A long-standing labelled indication supported by the registration programme. The label is candid that for some of the broader Candida uses in the same paragraph, including urinary tract infection and peritonitis, the supporting work was open and non-comparative in relatively small numbers of patients. Evidence: established. (Source 2)
• Approved, and still central, but as part of a combination rather than alone. The AMBITION trial showed high-dose fluconazole with flucytosine and a single dose of liposomal amphotericin B was non-inferior to the WHO standard, while the ACTA trial showed flucytosine clearly outperformed fluconazole as the amphotericin partner (31.1% versus 45.0% deaths at ten weeks). Evidence: established. (Source 2)
• On the label, but the comparative evidence is against it as first choice: anidulafungin succeeded in 75.6% of patients versus 60.2% for fluconazole (difference 15.4 points, 95% CI 3.9 to 27.0) in a randomised double-blind trial, and C. krusei is inherently resistant while C. auris is resistant in 87-100% of isolates. Evidence: disputed. (Source 4)
• A specific labelled prophylaxis indication in bone marrow transplantation. We did not retrieve the underlying trials in this pass, so this entry rests on the label as a position with its date and should be treated as thinner than the other indications here. Evidence: established. (Source 5)
• Off-label. A 322-infant randomised placebo-controlled trial cut invasive fungal infection from 13.2% to 2.7-3.8%, but overall mortality was unchanged and the trial was not powered to detect emerging resistance. Evidence: limited. (Source 6)
• Off-label in the US and not supported as a preferred option: in a network meta-analysis of 26 trials in 8,136 patients, fluconazole did not differ significantly from topical treatments, while continuous terbinafine and itraconazole were significantly better. Evidence: not-supported. (Source 7)

Interactions

• Cyclosporine (pharmacokinetic study): Fluconazole roughly doubles cyclosporine exposure, which matters a great deal in transplant recipients. Fourteen days of fluconazole 200 mg daily in eight kidney transplant recipients raised cyclosporine area under the curve by 92% on average and the trough level by 157%, with apparent oral clearance falling 45%. (Source 8)
• Warfarin and other coumarin anticoagulants (case reports): Fluconazole can lengthen the prothrombin time and cause bleeding. The evidence is postmarketing reports rather than a trial: bruising, nosebleeds, gastrointestinal bleeding, blood in the urine and melaena have been reported alongside rising prothrombin times. (Source 9)
• Statins (atorvastatin, simvastatin, fluvastatin) (label): Fluconazole slows the breakdown of several statins, raising the risk of muscle injury and rhabdomyolysis. The label frames this as a risk requiring symptom and creatine kinase monitoring rather than quantifying it. Limit: The label writes 'creatinine kinase' where the enzyme is creatine kinase (CK), the blood test used to detect muscle damage. The quotation keeps the label's spelling. (Source 10)
• Vitamin A (all-trans-retinoic acid) (case reports): The one documented vitamin interaction rests on a single patient: on combined all-trans-retinoic acid and fluconazole the patient developed pseudotumour cerebri, which resolved when fluconazole was stopped. The label says the combination may still be used, with the central nervous system risk in mind. Limit: The label writes 'all-trans-retinoid acid'; the chemical is all-trans-retinoic acid. The quotation keeps the label's spelling. This entry also rests on a single case report. (Source 11)
• Food (pharmacokinetic study): Food makes no difference. A food-effect study comparing fasting with a high-fat meal found drug exposure unaffected, which is why the label says fluconazole may be taken without regard to meals. No grapefruit interaction is described for fluconazole. (Source 12)
• Alcohol (theoretical): We found no ethanol-fluconazole interaction study in the label or in the trials we read, so any concern is theoretical rather than documented. The one adjacent fact on record is that the fatal liver reactions occurred predominantly in people taking multiple concomitant medicines known to be hepatotoxic, and alcohol is itself hepatotoxic. (Source 13)
• Other CYP2C9, CYP2C19 and CYP3A4 substrates generally (label): Fluconazole is a moderate inhibitor of CYP2C9 and CYP3A4 and a strong inhibitor of CYP2C19, so it can raise levels of many other drugs. The effect outlasts the course: enzyme inhibition persists four to five days after the last dose because of the long half-life. (Source 14)

Stopping it

• There is no dependence or withdrawal syndrome with fluconazole, but stopping suppressive treatment lets the infection return. In the recurrent-thrush trial, 90.8% of women were disease-free at six months on weekly fluconazole; by twelve months, six months after stopping, only 42.9% were, versus 21.9% on placebo. (Source 3)
• The drug's effect on other medicines does not stop when the course does: the enzyme-inhibiting effect persists four to five days after discontinuation because of fluconazole's long half-life. (Source 14)
• When fluconazole has injured the liver, stopping it is usually but not always enough for recovery, and the label asks for the drug to be stopped if signs of liver disease appear. (Source 15)

What goes wrong

Oral fluconazole in pregnancy was associated with about a 50% higher rate of spontaneous abortion than no exposure, and a 62% higher rate than topical azole exposure. (Source 16)

• Cohort study, Moderate certainty.
• Size: 3,315 exposed pregnancies versus 13,246 matched unexposed, from a cohort of 1,405,663 pregnancies.
• Who: Pregnant women in Denmark, 1997-2013.
• How long: Exposure from week 7 through 22 (abortion) or week 7 to birth (stillbirth)
• Result: Spontaneous abortion HR 1.48, 95% CI 1.23-1.77 (147/3,315 versus 563/13,246). Versus topical azoles HR 1.62, 95% CI 1.26-2.07. Stillbirth HR 1.32, 95% CI 0.82-2.14, not significant.
• Funding: not stated in the abstract (Danish register-based study)

There was a significantly increased risk of spontaneous abortion associated with fluconazole exposure (HR, 1.48; 95% CI, 1.23-1.77).

First-trimester oral fluconazole was associated with a small excess of musculoskeletal malformations, about 12 extra cases per 10,000 exposed pregnancies, and no excess of oral clefts or conotruncal defects. (Source 17)

• Cohort study, Moderate certainty.
• Size: 1,969,954 pregnancies, of which 37,650 (1.9%) exposed to oral fluconazole and 82,090 (4.2%) to topical azoles.
• Who: Medicaid-insured pregnancies in the United States, 2000-2014.
• How long: First-trimester exposure, outcomes diagnosed in the first 90 days after delivery.
• Result: Musculoskeletal malformations 52.1 (95% CI 44.8-59.3) versus 37.3 (33.1-41.4) per 10,000; adjusted RR 1.30 (1.09-1.56). Conotruncal RR 1.04 (0.70-1.55); oral clefts RR 0.91 (0.61-1.35). Dose-dependence: RR 1.29 (1.05-1.58) at 150 mg, 1.24 (0.93-1.66) above 150 up to 450 mg, and 1.98 (1.23-3.17) above 450 mg for musculoskeletal malformations.
• Funding: not stated in the abstract.

The risk of musculoskeletal malformations was 52.1 (95% confidence interval 44.8 to 59.3) per 10 000 pregnancies exposed to fluconazole versus 37.3 (33.1 to 41.4) per 10 000 pregnancies exposed to topical azoles.

Rare but sometimes fatal liver injury is recorded with fluconazole, with no consistent relationship to dose, duration, sex or age. (Source 13)

• Official position, Certainty not rated.
• Size: Combined clinical trials and postmarketing experience.
• Who: Patients taking fluconazole, with fatal cases predominantly in people with AIDS or malignancy on multiple concomitant medicines.
• How long: Not stated.
• Result: Spectrum from mild transient transaminase rises to clinical hepatitis, cholestasis and fulminant hepatic failure including fatalities. Transaminase elevations above eight times the upper limit of normal in approximately 1% of fluconazole-treated patients in clinical trials. Usually, but not always, reversible on discontinuation.
• Funding: not applicable (regulatory document)

The spectrum of these hepatic reactions has ranged from mild transient elevations in transaminases to clinical hepatitis, cholestasis and fulminant hepatic failure, including fatalities.

A single 150 mg dose for thrush caused more drug-related side effects than intravaginal treatment, 26% versus 16%. (Source 18)

• Official position, Low certainty.
• Size: 448 patients on fluconazole and 422 on active comparators in US comparative clinical studies.
• Who: Women with vaginal candidiasis.
• How long: Single dose.
• Result: Drug-related side effects 26% versus 16%. Commonest were headache 13%, nausea 7%, abdominal pain 6%; also diarrhoea 3%, dyspepsia 1%, dizziness 1%, taste perversion 1%. Mostly mild to moderate; rare angioedema and anaphylaxis in marketing experience.
• Funding: not applicable (regulatory document reporting manufacturer trials)

The most common treatment-related adverse events reported in the patients who received 150 mg single dose fluconazole for vaginitis were headache (13%), nausea (7%), and abdominal pain (6%).

On courses of a week or longer, about one in six patients had an adverse event and about 1.5% stopped treatment because of one. (Source 19)

• Official position, Low certainty.
• Size: Over 4,000 patients in trials of 7 days or more; 4,048 for the event list.
• Who: Patients treated for 7 or more days, including HIV-infected and non-HIV-infected.
• How long: 7 days or more.
• Result: 16% had adverse events; discontinuation 1.5% for clinical events and 1.3% for laboratory abnormalities. Events at 1% or more: nausea 3.7%, headache 1.9%, skin rash 1.8%, vomiting 1.7%, abdominal pain 1.7%, diarrhoea 1.5%. Adverse events more frequent in HIV-infected (21%) than non-HIV-infected (13%) patients.
• Funding: not applicable (regulatory document reporting manufacturer trials)

The following treatment-related clinical adverse events occurred at an incidence of 1% or greater in 4048 patients receiving DIFLUCAN for 7 or more days in clinical trials: nausea 3.7%, headache 1.9%, skin rash 1.8%, vomiting 1.7%, abdominal pain 1.7%, and diarrhea 1.5%.

Candida auris, ranked a critical priority pathogen by the WHO, is resistant to fluconazole in 87% to 100% of isolates. (Source 20)

• Systematic review, Moderate certainty.
• Size: 37 studies included in the final analysis, published 2011 to February 2021.
• Who: Patients with Candida auris infection worldwide.
• How long: Not applicable.
• Result: Fluconazole resistance 87-100%; voriconazole resistance 28-98%; amphotericin B 8-35%; echinocandins 0-8%. Overall and 30-day mortality with C. auris candidaemia 29-62% and 23-67%.
• Funding: WHO-commissioned review for the fungal priority pathogens list.

Limit of this finding: Every figure here is a range across the 37 included studies, not a pooled estimate, so none of these numbers should be quoted as 'the' rate. In the same list the review gives MIC90 values of 0.06 to 1.0 mg/l for isavuconazole, itraconazole and posaconazole; that is a laboratory concentration measurement, not a percentage of resistant isolates, and it is easy to misread as one because it sits among resistance percentages.

Resistance rates to fluconazole were as high as 87%-100%.

Resistance to fluconazole is a recognised and mechanistically understood problem, and the label states the frequency of its development is not known. (Source 21)

• Official position, Certainty not rated.
• Size: Not applicable.
• Who: Fungal isolates from treated infections.
• How long: Not applicable.
• Result: Point mutations in ERG11 reduce azole affinity, ERG11 overexpression raises target enzyme levels, and efflux pumps encoded by MDR and CDR genes pump the drug out; CDR upregulation can cause multi-azole resistance. The frequency of resistance development for the indicated fungi is stated to be unknown.
• Funding: not applicable (regulatory document)

A potential for development of resistance to fluconazole is well known. Fungal isolates exhibiting reduced susceptibility to other azoles may also show reduced susceptibility to fluconazole. The frequency of drug resistance development for the various fungi for which this drug is indicated is not known.

The label warns that peeling skin disorders have occurred on fluconazole, that fatal outcomes have been reported in people with serious underlying disease, and that the drug should be stopped if a rash appears or progresses. (Source 15)

• Official position, Certainty not rated.
• Size: Not stated; spontaneous reports.
• Who: Patients treated with fluconazole.
• How long: Not stated.
• Result: No rate is given. The label instructs close monitoring and discontinuation if lesions progress in deep seated infection, and discontinuation in superficial infection if a rash may be attributable to fluconazole.
• Funding: not applicable (FDA-approved label)

(3) Dermatologic: Exfoliative skin disorders during treatment with DIFLUCAN have been reported. Fatal outcomes have been reported in patients with serious underlying diseases.

What the evidence supports

A single 150 mg oral dose of fluconazole was slightly more effective than multiple-day topical treatment for early clinical cure of uncomplicated vaginal thrush. (Source 22)

• Meta-analysis, Moderate certainty.
• Size: 7,208 participants across 50 randomised studies.
• Who: Women with uncomplicated vulvovaginal candidiasis.
• How long: Early outcome 7-10 days, late outcome 24-35 days.
• Result: Early clinical cure pooled OR 1.9, 95% CI 1.31-2.74, I2=0% in pairwise analysis and OR 1.52, 95% CI 1.13-2.07 in the network. Late mycological cure OR 1.42, 95% CI 1-1.99. All treatments were above 75% effective against placebo.
• Funding: not stated.

Limit of this finding: The review calls single-dose fluconazole 'marginally superior' for late mycological cure on an odds ratio of 1.42 with a 95% confidence interval of 1 to 1.99. An interval whose lower bound sits exactly on 1 does not show a difference, so that particular ranking should not be read as a win for fluconazole. Fluconazole also does not top every ranking: multiple-day itraconazole scored best for relief of symptoms, both early and late. The review's own conclusion is that a strict hierarchy of these treatments is probably inappropriate because both oral and topical drugs work well.

Single-day use of 150 mg of fluconazole was slightly more effective than multiple-day topical therapy in early clinical cure both in pairwise (pooled odds ratio=1.9, 95% confidence interval=1.31-2.74, I2=0%) and network meta-analysis (odds ratio=1.52, 95% confidence interval=1.13-2.07) analyses.

Weekly fluconazole kept recurrent vaginal thrush away while it was being taken, but most of the benefit was lost once it stopped. (Source 3)

• Randomized trial, Moderate certainty.
• Size: 387 women randomised.
• Who: Women with recurrent vulvovaginal candidiasis in clinical remission after open-label induction.
• How long: Six months of weekly treatment, then six months of observation.
• Result: Disease-free at 6, 9 and 12 months: 90.8%, 73.2% and 42.9% with fluconazole versus 35.9%, 27.8% and 21.9% with placebo (P<0.001). Median time to recurrence 10.2 versus 4.0 months. No fluconazole resistance or C. glabrata superinfection detected. One withdrawal for headache.
• Funding: not stated in the abstract.

The proportions of women who remained disease-free at 6, 9, and 12 months in the fluconazole group were 90.8 percent, 73.2 percent, and 42.9 percent, as compared with 35.9 percent, 27.8 percent, and 21.9 percent, respectively, in the placebo group (P< 0.001).

A regimen built on high-dose fluconazole plus flucytosine with a single dose of liposomal amphotericin B was non-inferior to the WHO standard for HIV-associated cryptococcal meningitis and caused fewer severe adverse events. (Source 23)

• Randomized trial, High certainty.
• Size: 844 randomised, 814 in the intention-to-treat population.
• Who: HIV-positive adults with cryptococcal meningitis in five African countries.
• How long: 10 weeks.
• Result: Death at 10 weeks 24.8%, 95% CI 20.7 to 29.3) versus 117 (28.7%, 95% CI 24.4 to 33.4); difference -3.9 percentage points, upper boundary of the one-sided 95% CI 1.2 percentage points, within the 10-point non-inferiority margin, P<0.001 for non-inferiority. Grade 3 or 4 adverse events 50.0% versus 62.3%.
• Funding: European and Developing Countries Clinical Trials Partnership and others.

At 10 weeks, deaths were reported in 101 participants (24.8%; 95% confidence interval [CI], 20.7 to 29.3) in the liposomal amphotericin B group and 117 (28.7%; 95% CI, 24.4 to 33.4) in the control group (difference, -3.9 percentage points); the upper boundary of the one-sided 95% confidence interval was 1.2 percentage points (within the noninferiority margin; P<0.001 for noninferiority).

Prophylactic fluconazole reduced invasive fungal infection in very-low-birth-weight neonates, cutting it from 13.2% to under 4%. (Source 6)

• Randomized trial, Moderate certainty.
• Size: 322 infants weighing under 1500 g at birth, across eight Italian neonatal intensive care units.
• Who: Very-low-birth-weight neonates.
• How long: From birth to day 30 of life, or day 45 if under 1000 g.
• Result: Invasive fungal infection 2.7% (6 mg/kg) and 3.8% (3 mg/kg) versus 13.2% on placebo (P=0.005 and P=0.02). Colonisation 9.8% and 7.7% versus 29.2% (P<0.001)
• Funding: not stated in the abstract.

The incidence of invasive fungal infection was 2.7% in the 6-mg group and 3.8% in the 3-mg group, as compared with 13.2% in the placebo group (P=0.005 for the 6-mg group and P=0.02 for the 3-mg group vs. the placebo group).

In the two US trials behind the label, a single 150 mg fluconazole tablet cured vaginal thrush in just over half of the women assessed, the same proportion as seven days of intravaginal treatment. (Source 24)

• Randomized trial, Moderate certainty.
• Size: 870 women enrolled (448 fluconazole, 422 vaginal product); 674 evaluable at late follow-up.
• Who: Women with vaginal candidiasis in two US trials.
• How long: Assessed one month after treatment.
• Result: Therapeutic cure 55% in both arms. In the label's table the fluconazole column reads 448 enrolled, 347 (77%) evaluable, clinical cure 239/347 (69%), mycologic eradication 213/347 (61%), therapeutic cure 190/347 (55%); the vaginal product column reads 422 enrolled, 327 (77%) evaluable, 235/327 (72%), 196/327 (60%), 179/327 (55%)
• Funding: not applicable (FDA-approved label)

Limit of this finding: The label presents the per-arm numbers only as a table, so no single sentence in the label pairs a figure with its column. In plain words, the table has an unlabelled first column of row names and two result columns: the first result column is the single 150 mg fluconazole tablet and the second is the intravaginal product given nightly for 7 days. Clinical cure was 69% with fluconazole and 72% with the vaginal product, mycologic eradication 61% versus 60%, and therapeutic cure 55% in both. Those pairings are read off the table, not quoted from a sentence.

The therapeutic cure rate, defined as a complete resolution of signs and symptoms of vaginal candidiasis (clinical cure), along with a negative KOH examination and negative culture for Candida (microbiologic eradication), was 55% in both the fluconazole group and the vaginal products group.

What the evidence does not support

By the later follow-up there was no significant difference between oral and topical treatment for clinical cure of uncomplicated thrush, single-day or multiple-day. (Source 22)

• Meta-analysis, Moderate certainty.
• Size: 3,983 participants in the late-cure network.
• Who: Women with uncomplicated vulvovaginal candidiasis.
• How long: 24-35 days.
• Result: No significant differences in odds ratios of success between oral and topical treatment, as single or multiple-day therapy. The authors conclude a strict hierarchy of treatments is probably inappropriate.
• Funding: not stated.

Limit of this finding: The review calls single-dose fluconazole 'marginally superior' for late mycological cure on an odds ratio of 1.42 with a 95% confidence interval of 1 to 1.99. An interval whose lower bound sits exactly on 1 does not show a difference, so that particular ranking should not be read as a win for fluconazole. Fluconazole also does not top every ranking: multiple-day itraconazole scored best for relief of symptoms, both early and late. The review's own conclusion is that a strict hierarchy of these treatments is probably inappropriate because both oral and topical drugs work well.

In the evaluation of late clinical cure, there were no significant differences in the odds ratios of success between oral and topical treatment, either as single or multiple-day therapy (3983 subjects in the network).

The authors of that trial were explicit that weekly fluconazole reduces recurrence but does not achieve long-term cure. (Source 3)

• Randomized trial, Moderate certainty.
• Size: 387 women.
• Who: Women with recurrent vulvovaginal candidiasis.
• How long: 12 months.
• Result: 42.9% disease-free at 12 months on fluconazole versus 21.9% on placebo, after treatment stopped at 6 months.
• Funding: not stated in the abstract.

Long-term weekly treatment with fluconazole can reduce the rate of recurrence of symptomatic vulvovaginal candidiasis. However, a long-term cure remains difficult to achieve.

As the partner drug for amphotericin B in cryptococcal meningitis, flucytosine was clearly better than fluconazole, with about a third fewer deaths. (Source 25)

• Randomized trial, High certainty.
• Size: 721 patients randomised; 228 versus 224 in the partner-drug comparison.
• Who: HIV-infected adults with cryptococcal meningitis in Africa.
• How long: 10 weeks.
• Result: 71 deaths (31.1%) with flucytosine versus 101 deaths (45.0%) with fluconazole; hazard ratio for death at 10 weeks 0.62, 95% CI 0.45 to 0.84, P=0.002.
• Funding: independent (NIH-supported); ACTA trial.

As a partner drug with amphotericin B, flucytosine was superior to fluconazole (71 deaths [31.1%] vs. 101 deaths [45.0%]; hazard ratio for death at 10 weeks, 0.62; 95% confidence interval [CI], 0.45 to 0.84; P=0.002).

In a double-blind noninferiority trial for invasive candidiasis, mostly candidaemia, fluconazole was the less successful arm: anidulafungin met its noninferiority target and the observed difference favoured anidulafungin. (Source 4)

• Randomized trial, Moderate certainty.
• Size: 245 patients in the primary analysis.
• Who: Adults with invasive candidiasis, 89% with candidaemia only, 97% without neutropenia; C. albicans in 62%.
• How long: End of intravenous therapy, with later time points.
• Result: Global response success 75.6% with anidulafungin versus 60.2% with fluconazole; difference 15.4 percentage points, 95% CI 3.9 to 27.0. With one centre removed, 73.2% versus 61.1%, difference 12.1 points, 95% CI -1.1 to 25.3, which crosses zero. Death from all causes 31% fluconazole versus 23% anidulafungin, P=0.13. Adverse events similar between groups.
• Funding: not stated in the recorded passage.

Limit of this finding: This was a double-blind noninferiority trial: it was designed to test whether anidulafungin was not worse than fluconazole, and the authors' conclusion is exactly that. The 15.4 percentage point difference favouring anidulafungin should not be read as a superiority claim the authors made, and when one centre was removed the difference was 12.1 points with a 95% confidence interval of -1.1 to 25.3, which crosses zero.

At the end of intravenous therapy, treatment was successful in 75.6% of patients treated with anidulafungin, as compared with 60.2% of those treated with fluconazole (difference, 15.4 percentage points; 95% confidence interval [CI], 3.9 to 27.0).

That same neonatal trial showed no mortality benefit, and was not powered to detect emerging resistance. (Source 6)

• Randomized trial, Low certainty.
• Size: 322 infants.
• Who: Very-low-birth-weight neonates.
• How long: 30 to 45 days of prophylaxis.
• Result: Overall mortality similar among groups, as was cholestasis. No resistant Candida emerged, but the study lacked substantial power to detect such an effect.
• Funding: not stated in the abstract.

Overall mortality was similar among groups, as was the incidence of cholestasis.

For toenail fungal infection, fluconazole did not differ significantly from topical treatments, while continuous terbinafine and itraconazole did better. (Source 7)

• Meta-analysis, Moderate certainty.
• Size: 8,136 patients across 26 trials included in the odds ratios (77 RCTs screened)
• Who: People with toenail onychomycosis.
• How long: Trial durations varied.
• Result: Fluconazole, pulse terbinafine, pulse itraconazole and topical treatments did not differ significantly in odds of mycological cure; continuous terbinafine 250 mg and continuous itraconazole 200 mg were significantly better than topicals. Moderate to high quality evidence for mycological cure.
• Funding: not stated.

Fluconazole, pulse regimens of terbinafine and itraconazole, and topical treatments did not differ significantly in the odds of achieving mycological cure.

In those same trials the quarter of women with recurrent thrush did markedly worse on a single fluconazole dose than the three-quarters with occasional thrush, and the label says the numbers were too small to compare with vaginal treatment. (Source 24)

• Randomized trial, Low certainty.
• Size: About one quarter of the 870 enrolled women had recurrent vaginitis (four or more episodes in 12 months)
• Who: Women with recurrent vulvovaginal candidiasis within the two US registration trials.
• How long: Assessed one month after a single 150 mg dose.
• Result: Recurrent vaginitis subgroup: 57% clinical cure, 47% mycologic eradication, 40% therapeutic cure, against 80%, 67% and 59% in the acute vaginitis subgroup. The label states the recurrent subgroup was too small for meaningful comparison with vaginal products.
• Funding: not applicable (FDA-approved label)

Limit of this finding: These subgroup percentages were not planned comparisons and the label itself says the recurrent group was too small to compare with the vaginal products, so the gap between the two subgroups is a description of what happened in these trials, not a measured treatment difference.

The remaining one-fourth of enrolled patients had recurrent vaginitis (≥4 episodes/12 months) and achieved 57% clinical cure, 47% mycologic eradication, and 40% therapeutic cure.

Where the evidence is mixed

Fluconazole monotherapy for cryptococcal meningitis in AIDS was compared with amphotericin B in the registration programme, with high mortality in both arms and no clear winner. (Source 26)

• Official position, Low certainty.
• Size: 63 subjects on amphotericin B and 131 on fluconazole.
• Who: Patients with AIDS and cryptococcal meningitis.
• How long: Course of therapy.
• Result: Mortality among high-risk patients 33% (amphotericin B) versus 40% (fluconazole), p=0.58; overall deaths 9/63 (14%) versus 24/131 (18%), p=0.48. The label states optimal doses and regimens for high-risk patients remain to be determined.
• Funding: not applicable (regulatory document citing Saag et al., N Engl J Med 1992)

Limit of this finding: The two arms are very unequal in size, 63 patients on amphotericin B and 131 on fluconazole, and the label states the two death figures in that order without repeating which drug each belongs to. So 14% (9 of 63) is amphotericin B and 18% (24 of 131) is fluconazole; reversing the order reverses the finding. Neither difference was statistically significant.

Mortality among high risk patients was 33% and 40% for amphotericin B and DIFLUCAN patients, respectively (p=0.58), with overall deaths 14% (9 of 63 subjects) and 18% (24 of 131 subjects) for the 2 arms of the study (p=0.48).

Where the research disagrees

How safe a single 150 mg dose of fluconazole is in early pregnancy

• Molgaard-Nielsen and colleagues, JAMA 2016 (Danish national cohort), Register-based cohort of 1,405,663 pregnancies with propensity-score-matched comparators, including a topical-azole comparator group: There was a significantly increased risk of spontaneous abortion associated with fluconazole exposure (HR, 1.48; 95% CI, 1.23-1.77). (Source 16)
• Zhu and colleagues, BMJ 2020 (US Medicaid cohort), Population-based cohort of 1,969,954 pregnancies with propensity-score fine stratification; found no excess of oral clefts or conotruncal defects but a small excess of musculoskeletal malformations: Oral fluconazole use in the first trimester was not associated with oral clefts or conotruncal malformations, but an association with musculoskeletal malformations was found, corresponding to a small adjusted risk difference of about 12 incidents per 10 000 exposed pregnancies overall. (Source 17)
• FDA label for DIFLUCAN (SPL version 57, effective 2 April 2026), Regulatory position; acknowledges the epidemiological signal while noting the studies have limitations and the findings are unconfirmed in controlled trials: Epidemiological studies suggest a potential risk of spontaneous abortion and congenital abnormalities in infants whose mothers were treated with 150 mg of fluconazole as a single or repeated dose in the first trimester, but these epidemiological studies have limitations (Source 27)

Whether fluconazole is adequate treatment for serious invasive yeast infection

• FDA label for DIFLUCAN, Regulatory position, resting in part on open non-comparative studies in relatively small numbers of patients: In open noncomparative studies of relatively small numbers of patients, DIFLUCAN was also effective for the treatment of Candida urinary tract infections, peritonitis, and systemic Candida infections including candidemia, disseminated candidiasis, and pneumonia. (Source 2)
• Reboli and colleagues, N Engl J Med 2007, Randomised, double-blind, non-inferiority trial in 245 patients; anidulafungin outperformed fluconazole: At the end of intravenous therapy, treatment was successful in 75.6% of patients treated with anidulafungin, as compared with 60.2% of those treated with fluconazole (difference, 15.4 percentage points; 95% confidence interval [CI], 3.9 to 27.0). (Source 4)
• Day and colleagues (ACTA), N Engl J Med 2018, Randomised trial in 721 patients with cryptococcal meningitis; flucytosine superior to fluconazole as the amphotericin B partner: As a partner drug with amphotericin B, flucytosine was superior to fluconazole (71 deaths [31.1%] vs. 101 deaths [45.0%]; hazard ratio for death at 10 weeks, 0.62; 95% confidence interval [CI], 0.45 to 0.84; P=0.002). (Source 25)

How much

• Reference intake: There is no reference intake for fluconazole; it is a prescription antifungal and the dose is set by the prescriber according to the infection. As the label's position, vaginal candidiasis is treated with 150 mg as a single oral dose, while acute cryptococcal meningitis is treated with 400 mg on the first day followed by 200 mg once daily, for 10 to 12 weeks after the cerebrospinal fluid becomes culture negative. (Source 28)
• Upper limit: No tolerable upper intake level exists. The highest routine daily dose in the adult label sections we read is 400 mg once daily, used in cryptococcal meningitis at the prescriber's judgement; the label's pregnancy warning refers to a 400 to 800 mg/day range as high-dose therapy. Trials in cryptococcal meningitis have used 1200 mg daily. Reported as positions and trial doses only, not a recommendation. (Source 28)
• Studied: The AMBITION trial gave fluconazole 1200 mg per day for 14 days alongside flucytosine and a single 10 mg/kg dose of liposomal amphotericin B. (Source 23)
• Studied: The recurrent thrush trial used three 150 mg doses at 72-hour intervals to induce remission, then 150 mg weekly for six months. (Source 3)
• Studied: The neonatal prophylaxis trial randomised infants under 1500 g to fluconazole 6 mg/kg, 3 mg/kg, or placebo. (Source 6)
• Studied: The cyclosporine interaction study used fluconazole 200 mg daily for 14 days in kidney transplant recipients. (Source 8)

A common belief, and what the research shows

The belief: One fluconazole tablet is a harmless, universal cure for yeast infections, including in pregnancy.

What the research shows: It is a genuinely good single-dose treatment for simple vaginal thrush, but it is neither harmless nor universal. The label itself records that a single dose causes more side effects than topical treatment: "The overall incidence of side effects possibly related to DIFLUCAN was 26%. In 422 patients receiving active comparative agents, the incidence was 16%." In pregnancy the Danish national cohort found "There was a significantly increased risk of spontaneous abortion associated with fluconazole exposure (HR, 1.48; 95% CI, 1.23-1.77)." and a US cohort of nearly two million pregnancies found a small excess of musculoskeletal malformations. And for serious infection it is often the weaker drug: "As a partner drug with amphotericin B, flucytosine was superior to fluconazole (71 deaths [31.1%] vs. 101 deaths [45.0%]; hazard ratio for death at 10 weeks, 0.62; 95% confidence interval [CI], 0.45 to 0.84; P=0.002)."

Questions and answers

What is it?

Fluconazole is a synthetic triazole antifungal drug, the first of its subclass, supplied as tablets, an oral suspension and an intravenous solution. The label describes it as a white crystalline solid that is only slightly soluble in water and saline. It is a manufactured medicine, not a nutrient, a food component or a plant extract. (Source 29)

What does it do in the body?

It stops yeasts growing by blocking the fungal enzyme that makes ergosterol, the fat that fungal cell membranes need. Abnormal sterols build up instead, which the label links to the drug's fungistatic effect, and the equivalent human enzyme is much less sensitive to the drug. It is absorbed over 90% by mouth and has a half-life of about 30 hours, which is why a single dose can treat simple thrush. (Source 1)

Is it good or bad for you?

Good for the right infection, and not without cost. For simple vaginal thrush a single 150 mg dose was slightly better than multiple-day topical treatment for early clinical cure in a 50-trial network meta-analysis. The costs are a higher side-effect rate than topical treatment, rare but sometimes fatal liver injury, a pregnancy signal for spontaneous abortion and musculoskeletal malformations, and resistance: Candida auris is resistant in 87-100% of isolates and C. krusei inherently so. (Source 22)

How do you get more of it?

This question does not apply as it would to a nutrient; there is no reason to want more fluconazole than the prescribed course. Food makes no difference to how much is absorbed, and oral absorption is already over 90% compared with intravenous dosing, so neither diet nor timing changes exposure. Taking more raises harm without raising cure. (Source 12)

If it is harmful, what reduces it?

Fluconazole clears itself over a few days: the terminal half-life is about 30 hours, so most of a dose is gone within a week. The part that lingers is its effect on other drugs, which the label says persists four to five days after the last dose. If it has caused liver injury, the label asks for it to be stopped, and recovery is usual though not guaranteed. (Source 12)

Why might someone be low in it or missing it?

Nobody is naturally low in fluconazole. The real version of this question is why it sometimes fails, and the answer is resistance in the fungus rather than too little drug in the person: the label says resistance development is well known, arising from altered or overproduced target enzyme or from pumps that push the drug out of the fungal cell, and that the frequency of this happening is not known. (Source 21)

Which whole foods contain it or feed it?

No whole food contains fluconazole and no food feeds it; it is a manufactured triazole. Food is relevant only in that it does not matter: a study comparing fasting with a high-fat meal found exposure unaffected, so the drug may be taken with or without meals. (Source 12)

We searched: We read the DESCRIPTION and PHARMACOKINETICS sections of the DIFLUCAN label and searched PubMed for dietary sources of fluconazole; the only food-related data concern the absence of a food effect on absorption.

What happens if you do not have it?

Nothing, if there is no fungal infection to treat. Where there is, going without an effective antifungal can be lethal: in HIV-associated cryptococcal meningitis, roughly a quarter of patients died within ten weeks even on the better of two active regimens in the AMBITION trial. For recurrent thrush, stopping suppression returns most women to recurrence within months. (Source 23)

How can you test for it?

You do not test a person's fluconazole level in routine care; you test the fungus. Susceptibility testing of the isolate is the relevant test, and the label points to the FDA's susceptibility test interpretive criteria page rather than printing breakpoints, because they are revised. Its reliability is the usual one for laboratory susceptibility testing: it predicts activity against that isolate, not the clinical outcome in that patient. (Source 30)

References

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22. Am J Obstet Gynecol. Treatment of uncomplicated vulvovaginal candidiasis: topical or oral drugs? Single-day or multiple-day therapy? A network meta-analysis of randomized trials.. 2025. PMID 40157526, DOI 10.1016/j.ajog.2025.03.031. Read the source
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