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%), feces (2%)
- Mechanism of Action: Inhibits glutamate release and inhibits voltage-sensitive sodium channels