Valproic acid

Blood

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No Fasting Required

Details

Measures the concentration of valproic acid in the blood. Valproic acid is an anticonvulsant and mood-stabilizing drug

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Valproic Acid Test Information Guide

Why is it done?
- Measures serum concentration of valproic acid, an anticonvulsant medication used to treat epilepsy, bipolar disorder, and prevent migraines
- Monitors therapeutic drug levels to ensure effective seizure control and mood stabilization
- Detects potential toxicity or subtherapeutic levels that may require dose adjustment
- Performed at baseline, during dose titration, when symptoms change, and periodically during maintenance therapy
- Assesses compliance with medication regimen
- Evaluates for potential drug interactions when other medications are added or removed
Normal Range
- Therapeutic Range: 50-100 mcg/mL (350-700 µmol/L) Some sources report 50-125 mcg/mL depending on clinical indication
- Peak Level: 1-2 hours post-dose (immediate-release formulation) 3-4 hours post-dose (delayed-release formulation)
- Trough Level: Just before next scheduled dose
- Below 50 mcg/mL: Subtherapeutic; may not provide adequate seizure control
- Above 125 mcg/mL: Potentially toxic; increased risk of adverse effects
- Units: mcg/mL (micrograms per milliliter) or µmol/L (micromoles per liter)
Interpretation
- Therapeutic Level (50-100 mcg/mL): Optimal drug concentration for seizure control and mood stabilization; maintained with current dosing regimen
- Subtherapeutic Level (<50 mcg/mL): May indicate inadequate dosing, poor medication compliance, rapid metabolism, or drug interactions; risk of breakthrough seizures or symptom recurrence; dose increase recommended
- Supratherapeutic Level (>125 mcg/mL): Elevated concentration associated with toxicity; increased side effects including sedation, tremor, ataxia, nausea, and hepatotoxicity; dose reduction recommended
- Factors Affecting Levels:
  - Age: Elderly patients may have reduced clearance
  - Liver function: Impaired hepatic metabolism increases levels
  - Drug interactions: Inhibitors (aspirin, cimetidine) increase levels; inducers decrease levels
  - Protein binding: In hypoalbuminemia, free drug levels may be elevated despite normal total levels
  - Pregnancy: Increased metabolism; may require higher doses
  - Formulation type: Extended vs. immediate-release affects peak and trough timing
Associated Organs
- Primary Systems:
  - Central Nervous System: Primary therapeutic target for seizure disorders, bipolar disorder, and migraine prevention
  - Liver: Major site of metabolism; most critical organ for valproic acid toxicity
  - Pancreas: Risk of pancreatitis with chronic use
- Conditions Associated with Abnormal Results:
  - Elevated levels (>125 mcg/mL): Hepatic dysfunction, cirrhosis, renal impairment, polycystic ovary syndrome
  - Low levels (<50 mcg/mL): Hyperthyroidism, rapid metabolism, malabsorption disorders
  - Valproic acid-induced hepatotoxicity: Can range from asymptomatic elevation in liver enzymes to fulminant hepatic failure
  - Acute pancreatitis: Rare but serious complication with elevated amylase and lipase
  - Thrombocytopenia and hematologic disorders: Secondary to valproic acid therapy
- Toxicity and Complications:
  - Hepatotoxicity: Most serious concern; monitor liver function closely
  - Tremor, ataxia, and sedation: Occur at supratherapeutic levels
  - Teratogenic effects: Birth defects including neural tube defects when used in pregnancy
  - Hyperammonemia: Can occur with or without elevations in liver enzymes
Follow-up Tests
- Baseline and Periodic Monitoring:
  - Liver function tests (AST, ALT, total/direct bilirubin, albumin, alkaline phosphatase): Before starting therapy and at regular intervals (every 3-6 months)
  - Complete blood count (CBC): Monitor for thrombocytopenia and other hematologic abnormalities
  - Repeat valproic acid levels: 3-5 days after dose initiation or change; every 6-12 months during stable maintenance therapy
- When Levels are Abnormal:
  - Elevated levels: Comprehensive metabolic panel, liver function panel, ammonia level, direct and free valproic acid levels
  - Low levels: Assess medication compliance and timing of blood draw
  - Symptoms of toxicity: Prothrombin time (PT), amylase, lipase, coagulation studies
- Special Situations:
  - Pregnancy: More frequent monitoring (monthly); consultation with obstetrics and neurology recommended
  - Drug interactions: Recheck levels if other medications initiated or discontinued
  - Elderly or hepatic impairment: More frequent monitoring recommended (every 3 months)
Fasting Required?
- Fasting: No
- Food and beverages do not affect valproic acid serum levels; patient may eat and drink normally
- Timing Considerations:
  - Trough Level (preferred): Draw blood just before next dose; more consistent and stable measurement
  - Peak Level: 1-2 hours post-dose for immediate-release; 3-4 hours post-dose for extended-release formulations
  - Steady state: Achieved after 2-4 days of consistent dosing; wait at least 3-5 days after dose change before rechecking
- Medication and Special Instructions:
  - Continue taking valproic acid as prescribed; do not skip doses before testing
  - Do not take additional doses before the test
  - Inform healthcare provider of all medications and supplements; many drugs interact with valproic acid
  - Standard venipuncture preparation: No special skin preparation required
  - Specimen handling: Serum or plasma acceptable; send to laboratory promptly

How our test process works!