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Voriconazole EDTA Plasma

Blood
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Report in 144Hrs

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At Home

nofastingrequire

No Fasting Required

Details

Antifungal drug level.

₹7,696₹10,994

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Voriconazole EDTA Plasma - Comprehensive Test Information Guide

  • Why is it done?
    • Measures voriconazole serum concentration in EDTA (ethylenediaminetetraacetic acid) plasma to ensure therapeutic drug levels are achieved and maintained during antifungal therapy
    • Monitor patients receiving voriconazole for serious fungal infections such as invasive aspergillosis, candidiasis, and cryptococcosis to optimize therapeutic efficacy
    • Assess and prevent drug toxicity by maintaining voriconazole levels within the therapeutic window, particularly important given the drug's narrow therapeutic index
    • Evaluate variable bioavailability and metabolism due to genetic polymorphisms in CYP2C19, which affect individual drug clearance rates
    • Identify potential drug interactions or non-compliance affecting medication levels
    • Typically performed at steady state (typically after 4-7 days of therapy), before or after dose adjustments, and when clinical response is suboptimal
  • Normal Range
    • Therapeutic Range: 1.0 - 5.5 mg/L (or 2.0 - 5.5 mg/L depending on institution and clinical context)
    • Optimal Range for Most Indications: 2.0 - 4.0 mg/L (mcg/mL)
    • Units of Measurement: mg/L (milligrams per liter) or mcg/mL (micrograms per milliliter) - these are equivalent
    • Below 1.0 mg/L: Subtherapeutic - indicates insufficient drug levels, risk of treatment failure
    • Within 1.0 - 5.5 mg/L: Therapeutic - expected to provide efficacy with acceptable tolerability
    • Above 5.5 mg/L: Potentially Supratherapeutic - increased risk of adverse effects including neurotoxicity, hepatotoxicity, and visual disturbances
    • Interpretation varies based on infection type and patient factors; CNS infections may require higher levels (2.5-5.5 mg/L), while invasive aspergillosis typically targets 2.0-4.0 mg/L
  • Interpretation
    • Low Levels (Below 1.0 mg/L): Indicates inadequate drug concentration; suggests increased clearance, non-compliance, drug interactions reducing bioavailability, or rapid metabolism due to CYP2C19 polymorphisms; associated with higher risk of treatment failure and infection progression; dose adjustment upward is typically recommended
    • Therapeutic Levels (1.0-5.5 mg/L, ideally 2.0-4.0 mg/L): Optimal levels for most fungal infections; provides appropriate balance between efficacy and safety; indicates proper dosing regimen and good absorption; clinical response should be monitored concurrently; recommend continuation of current dosing and repeat monitoring in 7-10 days
    • High Levels (Above 5.5 mg/L, particularly >10 mg/L): Indicates excessive drug accumulation; risk of toxicity increases significantly, including CNS effects (hallucinations, confusion), hepatotoxicity (elevated liver enzymes), visual disturbances (photopsia), rash, and cardiac effects; may result from reduced clearance (hepatic or renal impairment), drug interactions (inhibitors of CYP2C19/3A4), or genetic poor metabolizers; dose reduction is strongly recommended; monitor for adverse effects
    • Factors Affecting Results:
    • CYP2C19 genetic polymorphisms (poor, intermediate, extensive, and ultra-rapid metabolizers) - major determinant of voriconazole clearance
    • Hepatic function - liver disease reduces metabolism and increases drug accumulation
    • Renal function - less critical for voriconazole elimination but important for overall drug metabolism
    • Drug interactions - inhibitors (azoles, protease inhibitors, SSRIs) increase levels; inducers (rifampin, phenytoin, carbamazepine) decrease levels
    • Route of administration - oral bioavailability variable (40-60%); intravenous administration more predictable
    • Food intake - increased absorption when taken with food (relevant for oral formulation)
    • Patient compliance - missed doses result in subtherapeutic levels
    • Sampling timing - levels should be drawn at steady state (after minimum 4 days of therapy) and ideally at trough (just before next dose) for consistency
  • Associated Organs
    • Primary Organ Systems Involved:
    • Hepatic System (Liver) - primary site of voriconazole metabolism via CYP2C19 and CYP3A4; drug accumulation in hepatic impairment; hepatotoxicity risk with elevated levels
    • Central Nervous System (CNS) - target site for CNS fungal infections (cryptococcal meningitis); neurotoxic effects at excessive levels including hallucinations, confusion, altered mental status, headaches
    • Visual System (Eyes) - visual disturbances (photopsia, blurred vision, changes in color perception) occur in 20-30% of patients, particularly with higher levels; generally reversible
    • Respiratory System - treats invasive aspergillosis and other pulmonary fungal infections
    • Renal System (Kidneys) - less involved in voriconazole elimination but important for overall clearance; impairment affects drug metabolism
    • Fungal Infections Treated/Monitored:
    • Invasive Aspergillosis - most common indication; life-threatening in immunocompromised patients
    • Candidiasis (esophageal, candidemia, other invasive forms) - particularly in immunocompromised populations
    • Cryptococcal Meningitis - CNS infection requiring adequate CNS penetration
    • Scedosporium and Fusarium Infections - serious infections in severely immunocompromised patients
    • Coccidioidomycosis and Blastomycosis - endemic fungal infections
    • Complications Associated with Abnormal Levels:
    • Low Levels: Persistent or progressive fungal infection, treatment failure, increased mortality risk
    • High Levels: Hepatotoxicity (elevated transaminases, jaundice), neurotoxicity (altered mental status, seizures), visual disturbances, QT prolongation, rash (including Stevens-Johnson syndrome), acute kidney injury
    • Allergic Reactions: Infusion reactions, hypersensitivity (rare)
  • Follow-up Tests
    • Recommended Follow-up Voriconazole Levels:
    • Repeat level 3-5 days after dose adjustment to confirm achievement of therapeutic range
    • Ongoing monitoring at 7-10 day intervals during long-term therapy (weeks to months)
    • Immediately if signs of toxicity develop (altered mental status, visual changes, hepatic symptoms)
    • After introduction of new interacting medications or dose changes
    • Liver Function Tests (LFTs):
    • Baseline AST, ALT, bilirubin, alkaline phosphatase before initiating therapy
    • Repeat at days 3-5 and weekly during treatment - hepatotoxicity can develop with elevated voriconazole levels
    • Renal Function Tests:
    • Baseline serum creatinine and BUN
    • Weekly monitoring during therapy - acute kidney injury reported with elevated levels
    • Ophthalmologic Evaluation:
    • Baseline eye examination before or early in treatment, particularly with high-dose therapy
    • Ophthalmology referral if patient reports visual changes or with supratherapeutic levels
    • Electrocardiogram (ECG):
    • Baseline ECG if high-dose therapy anticipated or supratherapeutic levels detected - assess for QT prolongation
    • CYP2C19 Pharmacogenetic Testing:
    • Consider if unexplained subtherapeutic or supratherapeutic levels - identifies poor, intermediate, extensive, or ultra-rapid metabolizers
    • Helps guide future dosing and predicts drug behavior in similar infections
    • Fungal Culture and Susceptibility Testing:
    • From blood, CSF, or tissue if clinically indicated to assess treatment response and identify organism resistance
    • Imaging Studies:
    • CT chest/thorax - to monitor resolution of invasive aspergillosis
    • MRI brain - for CNS infections (cryptococcal meningitis) to assess treatment response
    • Clinical Response Assessment:
    • Microbiological response - clearance of positive cultures, disappearance of antigen/PCR positivity
    • Clinical response - resolution of fever, improvement in symptoms, disappearance of radiographic infiltrates
  • Fasting Required?
    • Fasting Status: NO - fasting is not required for voriconazole plasma level measurement
    • Sample Collection Requirements:
    • Specimen Type: EDTA Plasma (ethylenediaminetetraacetic acid - lavender-top tube)
    • Volume Required: Typically 2-3 mL of whole blood for plasma separation
    • Timing: Draw at trough level (just before next scheduled dose) at steady state (after minimum 4 days of therapy, ideally day 5-7) - ensures most stable, consistent results for interpretation
    • Avoid sampling within 2 hours of IV infusion completion or within 1-2 hours of oral dose
    • Special Instructions for Oral Formulation:
    • Patients may take voriconazole dose either with or without food on day of testing - no restriction needed
    • However, consistency in food intake timing relative to dosing is preferred between measurement occasions for comparable results
    • Medications to Avoid Before Testing:
    • No medications need to be held or avoided before specimen collection
    • Continue voriconazole as prescribed - do not skip dose; draw blood at specified time relative to dosing
    • Note any concurrent medications affecting voriconazole metabolism (CYP2C19/3A4 inhibitors or inducers) for clinical interpretation
    • Storage and Handling:
    • Plasma must be separated from cells within 1-2 hours of collection
    • Freeze plasma at -20°C or lower if not analyzed immediately
    • Transport on ice or dry ice depending on laboratory requirements
    • Other Patient Preparation:
    • Maintain normal fluid intake - hydration status does not significantly affect test results
    • Inform laboratory of actual voriconazole dose, route (IV vs. oral), and exact time of last dose
    • Document collection time precisely for accurate interpretation relative to dosing schedule
    • Patient may recline or sit comfortably during venipuncture

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