III. Mechanism

  1. Phenyltriazine anticonvulsant

IV. Pharmacokinetics

  1. Oral Bioavailability: 98%
  2. Elimination Half-Life: 22 to 36 hours

VI. Adverse Effects: Other

  1. Serious skin rash (Incidence 0.08% in adults)
    1. Stevens Johnson Syndrome
    2. Toxic Epidermal Necrolysis
  2. Prolonged QRS Interval
    1. Increased risk of ventricular Arrhythmia or Cardiac Arrest
    2. Mechanism
      1. Sodium Channel Blocker
    3. Higher risk in underlying heart disease
      1. Coronary Artery Disease (prior Myocardial Infarction)
      2. Structural heart disease
      3. Atrioventricular Block
      4. Heart Failure
    4. Approach
      1. Avoid in high risk cardiovascular patients
      2. Consider baseline EKG in age over 60 years or Cardiovascular Risk Factors
      3. Avoid combining with other Sodium Channel Blockers
    5. References
      1. (2021) Presc Lett 28(6):34
  3. Aplastic Anemia
  4. Thrombocytopenia
  5. Neutropenia
  6. Pancytopenia
  7. Aseptic Meningitis
  8. Serotonin Syndrome

VIII. Dosing: Adults

  1. Initial: 25 mg every other day for 2 weeks
  2. Next: 25 mg orally daily for 2 weeks
  3. Target dose: 50-100 mg orally twice daily
  4. Maximum dose: 400 mg/day
  5. Precautions
    1. Slow titration over 6 weeks or more reduces the risk of Stevens-Johnson Syndrome
    2. Dosing adjustments are needed when used with agents listed under Drug Interactions

IX. Monitoring

  1. Obtain labs monthly for the first 2 months and then every 3 to 12 months
  2. Complete Blood Count
  3. Liver Function Test

X. Approach: Toxicity or Overdose

  1. Evaluate as Unknown Ingestion
    1. Obtain other toxicologic screening including Acetaminophen level, Serum Glucose
    2. Electrocardiogram
  2. Effects in Overdose
    1. Ventricular Dysrhythmia
      1. Lamictal inhibits voltage-gated Sodium channels
      2. Wide QRS Complex
        1. Treat with Sodium Bicarbonate ampules until QRS Complex narrows
    2. Serotonin Syndrome
      1. Lamictal inhibits Serotonin reuptake
    3. Neurologic Effects
      1. Sedation (most common finding in Overdose)
      2. Seizures
        1. Paradoxical (as Lamictal is foremost an anticonvulsant)
        2. Children may experience Seizures at doses >30 mg/kg
      3. Agitation
      4. Increased Deep Tendon Reflexes (hyperreflexia)
      5. Myoclonic Jerks
    4. Miscellaneous
      1. Nausea or Vomiting
  3. Management
    1. Activated Charcoal
      1. Consider if <1 hour from time of ingestion, and patient without aspiration risk
    2. QRS Widening
      1. See above (regarding bicarbonate)
    3. Seizures
      1. See Status Epilepticus
      2. Benzodiazepines
      3. Consider Propofol and intubation
      4. Consider Hemodialysis
  4. Disposition
    1. If asymptomatic at 4-6 hours after ingestion, may discharge home
  5. References
    1. Tomaszewski (2020) Crit Dec Emerg Med 34(1): 28

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LAMOTRIGINE 150 MG TABLET Generic $0.07 each
LAMOTRIGINE 200 MG TABLET Generic $0.08 each
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LAMOTRIGINE ER 300 MG TABLET Generic $2.99 each
LAMOTRIGINE ER 50 MG TABLET Generic $0.75 each
LAMOTRIGINE ODT 100 MG TABLET Generic $3.05 each
LAMOTRIGINE ODT 200 MG TABLET Generic $4.18 each
LAMOTRIGINE ODT 25 MG TABLET Generic $3.43 each
LAMOTRIGINE ODT 50 MG TABLET Generic $3.57 each
lamictal (on 1/1/2022 at Medicaid.Gov Survey of pharmacy drug pricing)
LAMICTAL 100 MG TABLET Generic $0.05 each
LAMICTAL 150 MG TABLET Generic $0.07 each
LAMICTAL 200 MG TABLET Generic $0.08 each
LAMICTAL 25 MG DISPER TABLET Generic $0.19 each
LAMICTAL 25 MG TABLET Generic $0.03 each
LAMICTAL ODT 100 MG TABLET Generic $3.05 each
LAMICTAL ODT 200 MG TABLET Generic $4.18 each
LAMICTAL ODT 50 MG TABLET Generic $3.57 each
LAMICTAL XR 100 MG TABLET Generic $1.26 each
LAMICTAL XR 200 MG TABLET Generic $1.08 each
LAMICTAL XR 300 MG TABLET Generic $2.99 each
LAMICTAL XR 50 MG TABLET Generic $0.75 each