Triazole antifungal agent

Fluconazole

Diflucan

Dosage form
Tablet
Available strengths
50 mg/5 mL (oral suspension, when reconstituted); 2 mg/mL (intravenous solution)
Drug class
Triazole antifungal agent
Common brand
Diflucan

Clinical overview. Fluconazole is a triazole antifungal medication used to treat oropharyngeal, esophageal, and systemic candida infections, cryptococcal meningitis, and to prevent candidiasis in bone marrow transplant patients. It can be taken with or without food and is available as an oral suspension or intravenous infusion, with the same daily dose used for either route. Fluconazole has extensive potential for drug interactions, including with warfarin, statins, and drugs that prolong the QT interval, and should generally be avoided during pregnancy.

Indication

Common therapeutic uses

  • Fluconazole treats oropharyngeal and esophageal candidiasis, yeast infections of the mouth, throat, and swallowing tube.
  • Fluconazole treats serious systemic candida infections, including infections of the urinary tract, abdominal cavity, and lungs.
  • Fluconazole treats cryptococcal meningitis, a serious fungal infection affecting the lining of the brain and spinal cord.
  • Fluconazole is used to prevent the recurrence of cryptococcal meningitis in patients with AIDS.
  • Fluconazole is used to reduce the risk of candida infections in patients undergoing bone marrow transplantation who are receiving chemotherapy or radiation therapy.

Pregnancy

Risk assessment and monitoring considerations

  • Fluconazole should not be used during pregnancy except for severe or potentially life-threatening fungal infections, where the benefit to the mother is judged to outweigh the risk to the baby.
  • Repeated or high-dose fluconazole use during the first trimester has been associated with an increased risk of miscarriage and a distinctive pattern of birth defects, including skull, facial, and bone abnormalities and heart defects.
  • Even low, single doses used during the first trimester have been linked in some studies to an increased risk of miscarriage and birth defects.
  • Women who become pregnant while taking fluconazole should notify their doctor immediately.

Breastfeeding

Infant exposure considerations

  • Fluconazole passes into breast milk at concentrations similar to those in the mother's blood, so breastfeeding is not recommended while taking this medication.

Geriatrics

Dosing and tolerability considerations

  • Fluconazole is generally well tolerated in patients 65 years of age and older.
  • Because older adults are more likely to have reduced kidney function, caution is needed and the dose should be adjusted based on kidney function; monitoring kidney function may be useful.
  • In bone marrow transplant patients, a higher rate of treatment discontinuation due to side effects was seen in older patients compared with younger patients.

Pediatrics

Use in children and adolescents

  • Fluconazole is approved for use in children, with dosing based on body weight for the same infections treated in adults.
  • Fluconazole has been shown effective for oropharyngeal candidiasis in children 6 months to 13 years of age, and for serious systemic candida and cryptococcal infections in children.
  • Effectiveness has not been established in infants younger than 6 months of age, although a small number of infants in this age range have been treated safely.

Dosage & Administration

Practical dosing and administration

  • Because oral absorption of fluconazole is rapid and nearly complete, the same daily dose is used whether it is given as oral suspension or by intravenous infusion.
  • For oropharyngeal candidiasis, the usual adult dose is taken once daily for at least 2 weeks; children receive a weight-based dose for the same duration.
  • For esophageal candidiasis, the usual adult dose is taken once daily for at least 3 weeks and for at least 2 weeks after symptoms resolve.
  • For serious systemic candida infections, the usual adult dose is taken once daily for at least 4 weeks and for at least 2 weeks after symptoms resolve; a loading dose of twice the daily dose is often given on the first day.
  • For cryptococcal meningitis, the usual adult dose is taken once daily for a minimum of 10 weeks; a lower maintenance dose is then used to prevent recurrence in patients with AIDS.
  • For prevention of candidiasis during bone marrow transplantation, the usual adult dose is taken once daily, started before the anticipated drop in white blood cell counts and continued for 7 days after counts recover.
  • The dose must be reduced in patients with impaired kidney function, based on creatinine clearance, after an initial loading dose; patients on hemodialysis receive their dose after each dialysis session.
  • The intravenous infusion should be given at a controlled, limited maximum rate to avoid infusing it too quickly.

Overdose

Recognizing and responding to overdose

If overdose is suspected, seek emergency medical attention immediately or contact your regional Poison Control Centre without delay.

  • Reports of fluconazole overdose have included hallucinations and paranoid behaviour.
  • Treatment of overdose is mainly supportive, including symptomatic care and gastric lavage if appropriate soon after ingestion.
  • A few hours of hemodialysis removes a substantial portion of the drug from the blood, which can be considered in severe cases.
  • Activated charcoal may help reduce absorption of drug that has not yet been absorbed.

Common side effects

Frequently reported tolerability concerns

  • Headache may occur.
  • Nausea may occur.
  • Abdominal pain may occur.
  • Diarrhea may occur.
  • Vomiting may occur.
  • Skin rash may occur.
  • Changes in liver enzyme blood tests may occur.
  • Dizziness may occur.
  • Taste changes may occur.
  • When used as a single dose for vaginal yeast infection, headache, nausea, and abdominal pain are the most commonly reported effects.

Serious side effects

Findings that may require urgent assessment

Serious side effects require immediate discussion with the prescriber or emergency care.

  • Rare but serious liver problems, including hepatitis, liver failure, and, very rarely, fatal liver injury, have been reported, mainly in patients with serious underlying illness taking multiple medications.
  • Serious skin reactions, including exfoliative skin conditions, Stevens-Johnson syndrome, toxic epidermal necrolysis, and DRESS syndrome, have rarely been reported and can be fatal in patients with serious underlying illness.
  • Fluconazole can prolong the heart's QT interval and, rarely, has been associated with a dangerous heart rhythm called torsade de pointes.
  • Severe allergic reactions, including anaphylaxis and swelling of the face or throat, have rarely been reported.
  • Adrenal gland problems (adrenal insufficiency) have been reported rarely.
  • Blood disorders, including low white blood cell counts and, rarely, agranulocytosis, and low platelet counts, have been reported.
  • Seizures have been reported rarely.
  • Seek urgent medical attention for yellowing of the skin or eyes, severe skin rash or blistering, a fast or irregular heartbeat, fainting, or signs of a severe allergic reaction.

Use with caution

Situations requiring closer assessment

  • Use with caution in patients with pre-existing liver disease; liver function should be monitored, and the drug stopped if signs of liver injury develop.
  • Use with caution in patients with a history of heart rhythm problems, structural heart disease, or slow heart rate, or in those taking other medications that can prolong the QT interval.
  • Use with caution in patients with electrolyte imbalances, such as low potassium or magnesium, which can increase the risk of heart rhythm problems.
  • Use with caution in patients with impaired kidney function, with dosage adjusted based on kidney function.
  • Use with caution in patients taking multiple other medications, given fluconazole's potential for drug interactions.
  • Use with caution in patients with HIV/AIDS or other serious underlying illness, who appear to have a higher rate of side effects.

Contraindications

Situations where therapy may be inappropriate

  • Contraindicated in patients with known hypersensitivity to fluconazole, other azole antifungals, or any ingredient in the formulation.
  • Contraindicated in combination with pimozide, due to the risk of dangerous heart rhythm problems.
  • Contraindicated in combination with quinidine, due to the risk of dangerous heart rhythm problems.
  • Contraindicated in combination with erythromycin, due to the increased risk of serious heart rhythm problems and sudden death.

Drug interactions

Clinically relevant combinations

  • Fluconazole is a moderate inhibitor of certain liver enzymes (CYP2C9 and CYP3A4) and a strong inhibitor of another (CYP2C19), so it can raise blood levels of many other medications; this effect can persist for several days after stopping fluconazole.
  • Combining fluconazole with warfarin or other coumarin-type blood thinners can increase bleeding risk and prolong clotting time; monitoring is recommended.
  • Combining fluconazole with certain statins, such as atorvastatin or simvastatin, increases the risk of muscle damage (myopathy and rhabdomyolysis).
  • Combining fluconazole with cyclosporine can significantly raise cyclosporine levels, requiring monitoring and possible dose adjustment.
  • Combining fluconazole with phenytoin can raise phenytoin levels.
  • Combining fluconazole with rifampin can lower fluconazole levels, which may require a higher fluconazole dose.
  • Combining fluconazole with oral diabetes medications called sulfonylureas can increase the blood-sugar-lowering effect and the risk of low blood sugar.
  • Combining fluconazole with certain short-acting benzodiazepines, such as midazolam or triazolam, can increase their sedative effect.
  • Combining fluconazole with carbamazepine can raise carbamazepine levels and increase the risk of toxicity.
  • Combining fluconazole with amiodarone or other drugs that prolong the QT interval can increase the risk of dangerous heart rhythm problems.
  • Combining fluconazole with certain opioid pain medicines, such as fentanyl or methadone, can increase their blood levels and the risk of breathing problems.
  • Combining fluconazole with ibuprofen or other NSAIDs metabolized in a similar way can raise their blood levels.
  • Combining fluconazole with losartan can reduce its blood-pressure-lowering effect.

Food interactions

Meal-related administration

  • Fluconazole can be taken with or without food; absorption is not significantly affected by food.

Time of administration

Practical scheduling

  • Fluconazole oral suspension can be taken at any time of day, with or without food, and should be shaken well before each use.
  • The intravenous form is given by a healthcare professional at a controlled infusion rate and is not affected by meal timing.

Storage

Product handling

  • Store fluconazole powder for oral suspension at room temperature (15-30°C) before mixing; after mixing with water, store the suspension between 5-30°C, protected from freezing, shake well before each use, and discard any unused portion after 14 days.
  • Store fluconazole solution for intravenous infusion at room temperature (15-30°C) and do not freeze.

Patient take-away

Key counselling points for a quick closing summary

  • Fluconazole is an effective antifungal medication, but the length of treatment can be several weeks depending on the type of infection being treated.
  • Fluconazole has many potential drug interactions; tell your pharmacist or doctor about all other medications you take.
  • Report yellowing of the skin or eyes, severe rash, or an irregular heartbeat to a healthcare professional right away.

References

Source material and product information

  1. Health Canada Product Monograph — Fluconazole

For professional reference. Confirm patient-specific decisions against the current approved product monograph and applicable clinical guidance.

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