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Lamotrigine

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Lamotrigine, Lamictal

  • Mechanism
  1. Phenyltriazine anticonvulsant
  • Pharmacokinetics
  1. Oral bioavailability: 98%
  2. Elimination half-life: 22 to 36 hours
  • 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
  • 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
  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