Voriconazole Drug Profile

What is Voriconazole?

Voriconazole is a prescription antifungal medication belonging to the azole class of drugs. It is used to treat serious fungal infections, particularly those that are invasive or life-threatening. This medication is typically reserved for severe infections that may not respond to other antifungal treatments.

Uses

Voriconazole is approved for treating several serious fungal infections:

• Invasive aspergillosis: A potentially fatal infection caused by Aspergillus fungi that can affect the lungs, brain, and other organs
• Candidemia: Bloodstream infections caused by Candida yeasts, particularly in non-neutropenic patients
• Esophageal candidiasis: Fungal infections of the esophagus caused by Candida species
• Serious Candida infections: Including infections of the abdomen, kidney, bladder wall, and wounds
• Scedosporiosis and fusariosis: Rare but serious infections in patients who cannot tolerate or do not respond to other antifungal therapy

How it works

Voriconazole works by inhibiting an enzyme called 14-alpha-demethylase, which is essential for fungal cell membrane formation. By blocking this enzyme, the drug prevents fungi from producing ergosterol, a crucial component of their cell walls. This disruption weakens the fungal cell membrane, ultimately leading to cell death and elimination of the infection.

Side effects

Common side effects include:

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• Visual disturbances (blurred vision, color changes, light sensitivity)
• Nausea and vomiting
• Skin rash
• Headache
• Dizziness
• Fever
• Diarrhea
• Abdominal pain

Serious side effects requiring immediate medical attention:

• Severe liver problems (jaundice, dark urine, severe fatigue)
• Serious skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis)
• Heart rhythm abnormalities (QT prolongation)
• Severe allergic reactions
• Kidney problems

Warnings and precautions

• Liver monitoring: Regular liver function tests are required as voriconazole can cause serious liver damage, including hepatitis and liver failure
• Visual disturbances: Patients should avoid driving or operating machinery if experiencing visual side effects, which are common but usually reversible
• Pregnancy and breastfeeding: May cause harm to unborn babies and should be used only when potential benefits outweigh risks; not recommended during breastfeeding
• Heart conditions: Use with caution in patients with heart rhythm disorders, as the drug can prolong QT interval
• Sun exposure: Patients should avoid prolonged sun exposure and use sunscreen, as the medication increases photosensitivity and risk of skin cancer with long-term use

Interactions

Voriconazole has numerous significant drug interactions due to its effects on liver enzymes:

• Warfarin: Increases bleeding risk by enhancing warfarin’s blood-thinning effects
• Rifampin and rifabutin: Significantly reduce voriconazole levels, making it less effective
• Phenytoin: Reduces voriconazole effectiveness while increasing phenytoin levels
• Cyclosporine and tacrolimus: Increases levels of these immunosuppressants, requiring dose adjustments
• Statins (simvastatin, lovastatin): Increases risk of muscle toxicity
• Benzodiazepines: Enhances sedative effects of drugs like midazolam and triazolam
• Proton pump inhibitors: May reduce voriconazole absorption when taken together
• St. John’s Wort: Significantly reduces voriconazole levels and should be avoided

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Dosage

Voriconazole dosing varies significantly based on the type and severity of infection, patient weight, and whether given orally or intravenously. Typical adult dosing begins with a loading dose of 6 mg/kg intravenously every 12 hours for the first day, followed by a maintenance dose of 4 mg/kg every 12 hours. For oral administration, the usual maintenance dose is 200-300 mg twice daily, depending on patient weight. Doses must be taken at least one hour before or after meals for optimal absorption. All dosing should be individualized and determined by a healthcare provider based on the specific infection being treated, patient response, and blood level monitoring when available.

Sources: FDA DailyMed drug labels (public domain), BNF, WHO Essential Medicines List. This article is for informational purposes only and does not constitute medical advice. Always consult your healthcare provider before starting or stopping any medication.

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