Indications
Lamotrigine is an antiepileptic drug (AED) indicated for:
Epilepsy (adjunctive therapy in patients aged 2 years and older):
- Partial: Onset seizures.
- Primary generalized tonic: Clonic seizures.
- Generalized seizures of Lennox: Gastaut syndrome.
Epilepsy (monotherapy in patients aged 16 years and older).
Bipolar disorder in patients aged 18 years and older.
Dosage & Administration
Monotherapy of seizures (adult and child over 16 years): Initially 25 mg once daily for 14 days, then 50 mg once daily for further 14 days, then increased by maximum 50 mg/day every 7-14 days; usual maintenance dose 225-375 mg/day in 1-2 divided doses.
Adjunctive therapy of seizures with Valproate:
- Adult and child over 12 years: Initially 25 mg on alternate days for 14 days, then 25 mg once daily for further 14 days, thereafter increased by maximum 25-50 mg/day every 7-14 days; usual maintenance, 100-200 mg/day in 1-2 divided doses.
- Child 2-12 years: Initially 150 mcg/kg/day in 1-2 divided doses for 14 days (those weighing under 13 kg may receive 2 mg on alternate days for first 14 days), then 300 mcg/kg/day in 1-2 divided doses for further 14 days, thereafter increased by maximum 300 mcg/kg/day every 7-14 days; usual maintenance 1-3 mg/kg/day in 1-2 divided doses.
Adjunctive therapy of seizures (with enzyme inducing drugs e.g., Carbamazepine, Phenytoin, Phenobarbital, or Primidone) without Valproate:
- Adult and child over 12 years: Initially 50 mg once daily for 14 days, then 50 mg twice daily for further 14 days, thereafter increased by maximum 100 mg/day in every 7-14 days; usual maintenance 300-500 mg daily in 2 divided doses.
- Child 2-12 years: Initially 600 mcg/kg/day in 2 divided doses for 14 days, then 1.2 mg/kg/day in 2 divided doses for further 14 days, thereafter increased by maximum 1.2 mg/kg/day in every 7-14 days; usual maintenance 5-15 mg/kg/day in 2 divided doses (maximum 400 mg/day in 2 divided doses).
Monotherapy therapy of bipolar disorder (without enzyme inducing Drugs) without Valproate:
- Adult over 18 years: Initially 25 mg once daily for 14 days, then 50 mg once daily for further 14 days, then 100 mg once daily for further 7 days; usual maintenance dose 200 mg once daily; maximum 200 mg daily.
Adjunctive therapy of bipolar disorder with valproate:
- Adult over 18 years: Initially 25 mg on alternate days for 14 days, then 25 mg once daily for further 14 days, then 50 mg once daily for further 7 days; usual maintenance dose 100 mg daily; maximum 100 mg daily.
Adjunctive therapy of bipolar disorder (with enzyme inducing drugs with enzyme inducing drugs e.g., Carbamazepine, Phenytoin, Phenobarbital, or Primidone) without Valproate:
- Adult over 18 years: Initially 50 mg once daily for 14 days, then 50 mg twice daily for further 14 days, then 100 mg twice daily for further 7 days, then 150 mg twice daily for further 7 days; usual maintenance 200 mg twice daily
Interaction
- Valproate increases lamotrigine concentrations more than 2-fold.
- Carbamazepine, phenytoin, phenobarbital, primidone, and rifampin decrease lamotrigine concentrations by approximately 40%.
- Estrogen-containing oral contraceptives decrease lamotrigine concentrations by approximately 50%.
- Protease inhibitors lopinavir/ritonavir and atazanavir/lopinavir decrease lamotrigine exposure by approximately 50% and 32%, respectively.
Side Effects
Adult: Dizziness, headache, diplopia, ataxia, nausea, blurred vision, somnolence, rhinitis, pharyngitis, and rash.
Children: Vomiting, diarrhea, infection, fever, abdominal pain, and tremor.
Pregnancy & Lactation
Pregnancy category C. Either studies in animals have revealed adverse effects on the fetus (teratogenic or embryocidal or other) and there are no controlled studies in women or studies in women and animals are not available. Drugs should be given only if the potential benefit justifies the potential risk to the fetus.
Nursing Mothers: Lamotrigine is present in milk from lactating women taking Lamotrigine.
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