Home Drug Guide Voriconazole

Drug Guide

Generic Name

Voriconazole

Brand Names Vfend

Classification

Therapeutic: Antifungal

Pharmacological: Triazole antifungal

FDA Approved Indications

  • Invasive aspergillosis
  • Serious infections caused by Scedosporium apiospermum and Fusarium spp.
  • Vaginal candidiasis (not first-line)

Mechanism of Action

Voriconazole inhibits fungal cytochrome P450-dependent 14α-lanosterol demethylation, a key step in ergosterol synthesis, leading to increased membrane permeability and fungal cell death.

Dosage and Administration

Adult: Loading dose of 6 mg/kg IV every 12 hours for two doses, followed by 4 mg/kg IV every 12 hours; oral dose is 200 mg twice daily.

Pediatric: Dose varies based on weight and age; typically, 7 mg/kg IV every 12 hours for two doses, then 3 mg/kg IV every 12 hours; oral dosing of 200 mg twice daily.

Geriatric: No specific adjustment, but caution advised due to increased risk of adverse effects.

Renal Impairment: No adjustment for mild; use caution for moderate to severe—dose adjustments may be necessary.

Hepatic Impairment: Initial dose reduction recommended for severe hepatic impairment.

Pharmacokinetics

Absorption: Good oral bioavailability (~96%)

Distribution: Wide tissue distribution, high CSF penetration

Metabolism: Primarily via hepatic CYP2C19, CYP2C9, CYP3A4

Excretion: Mostly as metabolites via urine and feces

Half Life: First half-life approximately 6 hours; steady-state usually reached in 2 days with chronic dosing.

Contraindications

  • History of hypersensitivity to voriconazole or other azoles

Precautions

  • Monitor for hepatotoxicity, visual changes, skin reactions, and drug interactions.
  • Use with caution in hepatic impairment, monitor liver function tests regularly.
  • Pregnancy Category D—risk-benefit analysis required.
  • Lactation: unknown safety; avoid breastfeeding during treatment.

Adverse Reactions - Common

  • Visual disturbances (blurriness, color vision change) (frequent)
  • Liver enzyme elevations (frequent)
  • Skin rash (frequent)
  • Nausea and vomiting (common)

Adverse Reactions - Serious

  • Stevens-Johnson syndrome (rare)
  • Hepatotoxicity leading to liver failure (rare)
  • QT prolongation leading to arrhythmias (rare)
  • Hallucinations, confusion, or neurotoxicity (especially at high doses) (rare)

Drug-Drug Interactions

  • CYP3A4 inhibitors or inducers (e.g., rifampin, carbamazepine, erythromycin)
  • Other drugs prolonging QT interval (e.g., quinidine, amiodarone)

Drug-Food Interactions

N/A

Drug-Herb Interactions

N/A

Nursing Implications

Assessment: Monitor liver function tests, renal function, visual acuity, and QT interval.

Diagnoses:

  • Risk for hepatotoxicity
  • Risk for QT prolongation
  • Potential neurotoxicity

Implementation: Ensure correct dosing, monitor for adverse reactions, educate patient about visual and skin changes, and drug interactions.

Evaluation: Assess for resolution of infection, monitor for adverse effects, ensure liver function remains within normal limits.

Patient/Family Teaching

  • Report visual changes, skin rashes, or unusual symptoms immediately.
  • Take medication with food or without food, as directed.
  • Avoid driving or operating machinery if experiencing visual disturbances.
  • Inform healthcare provider of all medications being taken to avoid interactions.

Special Considerations

Black Box Warnings:

  • Risk of hepatotoxicity, QT prolongation, and allergic reactions

Genetic Factors: CYP2C19 polymorphisms can affect metabolism and serum levels (poor vs. extensive metabolizers).

Lab Test Interference: Possible laboratory interference with bilirubin and liver function tests.

Overdose Management

Signs/Symptoms: Nausea, vomiting, visual disturbances, neurological symptoms, elevated liver enzymes.

Treatment: Supportive care, activated charcoal if ingestion recent, and monitoring; hemodialysis unlikely to remove drug effectively.

Storage and Handling

Storage: Store at 20-25°C (68-77°F); protect from light.

Stability: Stable until expiration date when stored properly.

🛡️ 5 Critical Medication Safety Tips for Nurses

1

Triple-Check High-Risk Medications

Always have another nurse verify insulin, heparin, warfarin, and chemotherapy drugs. These "high-alert" medications cause the most serious errors. Check concentration, dose calculation, and pump settings twice.

2

Know Look-Alike, Sound-Alike Drugs

Common mix-ups: hydromorphone/morphine, Celebrex/Celexa, Zyprexa/Zyrtec. Always use BOTH generic and brand names, read labels twice, and use barcode scanning when available. One wrong letter can be fatal.

3

Assess Before AND After Giving Meds

Check vitals before cardiac meds, pain levels before analgesics, and blood glucose before insulin. Always reassess within 30 minutes to evaluate effectiveness and watch for adverse reactions.

4

Watch for Drug Interactions

Common dangerous combinations: warfarin + aspirin (bleeding), ACE inhibitors + potassium (hyperkalemia), digoxin + diuretics (toxicity). Always check drug interactions before administering new medications.

5

Educate Your Patients

Teach patients medication names, purposes, major side effects, and what to report. Informed patients catch errors and improve compliance. Always encourage questions - an educated patient is a safer patient.

⚡ Remember: When in doubt, don't give it out! It's always safer to double-check than regret later.

⚠️ Medical Disclaimer

This drug guide is for educational purposes only and is NOT intended for clinical use. Always consult current prescribing information, healthcare providers, and institutional protocols before administering any medication. Do not use this information for patient care decisions.