Fluconazole

Fluconazole is an antimycotic (antifungal agent) from the triazole group. It is used to treat fungal infections, including vaginal yeast infections (vaginal candidiasis), thrush in the mouth, and systemic fungal infections.

For an uncomplicated vaginal yeast infection, a single 150 mg capsule is usually sufficient. The active ingredient is taken by mouth and is distributed throughout the body via the bloodstream – it also reaches the vaginal mucosa.

Well-known brand names are Diflucan® and numerous generics.

Fluconazole inhibits fungal cells in a targeted way:

Mechanism of action:

• Inhibits the enzyme lanosterol 14α-demethylase
• This enzyme is required for ergosterol synthesis
• Ergosterol is an essential component of the fungal cell membrane
• Without ergosterol, the membrane becomes permeable and the fungus dies

Spectrum of activity:

• Candida albicans (most common cause of vaginal yeast infections)
• Other Candida species
• Cryptococcus
• Dermatophytes

Selectivity: Fluconazole acts more selectively on the cytochrome P450 enzymes of fungi than on those of humans.

Fluconazole is suitable for:

• Women with an acute vaginal yeast infection
• Recurrent vaginal yeast infections (prophylaxis)
• Thrush (fungal infection of the mouth/throat)
• Systemic fungal infections

Note on local therapy:

• For the treatment of acute or recurrent vaginal yeast infections, fluconazole is used when local therapy is not suitable

Not suitable:

• If the diagnosis is uncertain
• Bacterial vaginosis (different pathogen)
• Pregnancy (only if there is an urgent indication)

For an uncomplicated vaginal yeast infection:

• 150 mg as a single dose

For recurrent vaginal yeast infections:

• Initially: 150 mg on days 1, 4, and 7
• Then: 150 mg once a week for 6 months

For oral thrush:

• Initially: 200-400 mg on day 1
• Then: 100-200 mg once daily
• Duration: 7-21 days, until the oral thrush has cleared

Available strengths:

• 50 mg capsules
• 100 mg capsules
• 150 mg capsules
• 200 mg capsules

How to take:

• Swallow the capsule whole, without chewing, with water
• With or without food

For an acute vaginal yeast infection:

• Take one 150 mg capsule
• The effect sets in within 24-48 hours
• Symptoms usually improve within 24 hours

Important:

• Take the entire prescribed amount
• Even if the symptoms improve quickly
• The partner usually does not need to be treated as well

Fluconazole must not be taken in cases of:

• Hypersensitivity to fluconazole or other azole antifungals
• Concurrent use of terfenadine, astemizole, cisapride, pimozide, quinidine (QT prolongation)

Caution is needed in cases of:

• Liver disease
• Renal insufficiency (dose adjustment)
• Cardiac arrhythmias
• Electrolyte disturbances

Pregnancy: The single 150 mg dose should be avoided during pregnancy. Observational studies suggest a possibly increased risk of miscarriage if fluconazole is used in the first or second trimester of pregnancy. With use in the first trimester, studies observed an increased risk of heart defects and a slightly increased risk of musculoskeletal birth defects, the latter already at 150 mg and more so at higher doses. Local therapy should be preferred.

Breastfeeding: Passes into breast milk. A single dose is possible; for longer treatment, breastfeeding should be interrupted.

Common (1-10%):

• Headache
• Abdominal pain
• Diarrhea
• Nausea
• Vomiting
• Skin rash
• Elevated liver enzymes

Uncommon (0.1-1%):

• Taste disturbances
• Dizziness

Rare:

• Severe skin reactions (Stevens-Johnson syndrome)
• Liver damage
• QT prolongation
• Anaphylaxis

With a single dose: The side effects of a single 150 mg dose are usually mild and temporary.

Contraindicated with:

• Terfenadine, astemizole (antihistamines)
• Cisapride (prokinetic agent)
• Pimozide, quinidine (QT prolongation)

Dose adjustment needed with:

• Warfarin – increased tendency to bleed (monitor INR)
• Oral antidiabetic drugs – hypoglycemia possible
• Cyclosporine, tacrolimus – increased levels
• Statins – increased risk of rhabdomyolysis
• Benzodiazepines – increased sedation

Fluconazole inhibits CYP2C9 and CYP3A4, so many interactions are possible. If you take long-term medication, inform your doctor.