Lamotrigine

General

• Type: Anticonvulsants
• Dosage Forms: 5mg, 25mg, 50mg, 100mg, 150mg, 200mg
• Common Trade Names: LaMICtal (ODT, Starter, XR)

Adult Dosing

• Lennox-Gaustaut: Oral (Immediate release formulation)
  • Non-enzyme inducing AED adjuncts: Week 1-2, 25mg qday, week 3-4, 50mg qday, then increased by 50mg qday every 1-2 weeks; maintenance 225-375mg daily in 2 divided doses
  • Valproate adjunct: Week 1-2, 25mg qod, week 3-4, 25mg qday, then increased by 25-50mg qday every 1-2 weeks; maintenance 100-400mg daily
  • Enzyme inducing AED adjunct: Week 1-2, 50mg qday, week 3-4, 50mg bid, then increased by 100mg qday every 1-2 weeks; maintenance 300-500mg daily in 2 divided doses

• Partial seizures and primary generalized tonic-clonic seizures
  • Immediate release formulation: same as for Lennox-Gaustaut dosing
  • Extended release formulation:
    • Non-enzyme inducing AED adjuncts: Week 1-2, 25mg qday, week 3-4, 50mg qday, week 5, 100mg qday, week 6, 150mg qday, week 7, 200mg qday, week 8 and beyond, dose increases should not exceed 100mg qday at weekly intervals; maintenance 300-400mg daily
    • Valproate adjunct: Week 1-2, 25mg qod, week 3-4, 25mg qday, week 5, 50mg qday, week 6, 100mg qday, week 7, 150mg qday, week 8 and beyond, does increases should not exceed 100mg qday at weekly intervals; maintenance 200-250mg daily
    • Enzyme inducing AED adjunct: Week 1-2, 50mg qday, week 3-4, 100mg qday, week 5, 200mg qday, week 6, 300g qday, week 7, 400mg qday, week 8 and beyond, dose increases should not exceed 100mg qday at weekly intervals; maintenance 400-600mg daily

Pediatric Dosing

• Increased risk of developing serious skin rashes
• Oral
  • Children 2-12 years: Immediate release formulation
  • Non-enzyme inducing AED adjuncts: Week 1-2, 0.3mg/kg/day, week 3-4, 0.6mg/kg/day, then increased by 0.6mg/kg/day every 1-2 weeks; maintenance 4.5-7.5mg/kg/day
  • Valproate adjunct: Week 1-2, 0.15mg/kg/day, week 3-4, 0.3mg/kg/day, then increased by 0.3mg/kg/day every 1-2 weeks; maintenance 1-5mg/kg/day
  • Enzyme inducing AED adjunct: Week 1-2, 0.6mg/kg/day, week 3-4, 1.2mg/kg/day, then increased by 1.2mg/kg/day every 1-2 weeks; maintenance 5-15mg/kg/day
  • Adolescents >12 years: Refer to adult dosing

Special Populations

• Pregnancy Rating: C
• Lactation: 50% enters breast milk. Apnea, drowsiness, poor sucking.
• Renal Dosing: Decreased dosage may be effective; no adequately studied.
• Hepatic Dosing
  • Mild: no adjustment
  • Mod-severe without ascites: Decrease by 25%
  • Mod-severe with ascites: Decrease by 50%

Contraindications

• Allergy to class/drug

Adverse Reactions

Serious

• Serious skin reactions, Stevens-Johnson Syndrome and Toxic Epidermal Necrolysis
• Suicidal ideation
• Hypersensitivity reaction

Common

• Nausea, vomiting, abdominal pain
• Chest pain, edema
• Insomnia, somnolence, fatigue, dizziness
• Rash
• Dysmenorrhea
• Rhinitis
• Blurry vision
• Panctytopenia

Pharmacology

• Half-life: 25-33 hours
• Metabolism: Hepatic and renal
• Excretion: Urine (94%), fecers (2%)
• Mechanism of Action: Inhibits glutamate release and inhibits voltage-sensitive sodium channels

References

Authors

Ami Yamamoto, Neil Young, Ross Donaldson, Daniel Ostermayer