What is the dosage and usage of Lamictal (lamotrigine) for epilepsy and bipolar disorder?

Lamotrigine (Lamictal) Dosage and Usage for Epilepsy and Bipolar Disorder

For epilepsy, lamotrigine should be initiated at 25 mg daily for 2 weeks, then increased to 50 mg daily for 2 weeks, followed by 100 mg daily for 1 week, and then increased by 100 mg weekly until reaching the maintenance dose of 300-500 mg daily in divided doses. For bipolar disorder, start at 25 mg daily for 2 weeks, then 50 mg daily for 2 weeks, followed by 100 mg daily for 1 week, and then increased by 50 mg weekly until reaching the maintenance dose of 200 mg daily. 1, 2

Dosing for Epilepsy

Initial Titration Schedule (Adults)

• Week 1-2: 25 mg once daily
• Week 3-4: 50 mg once daily
• Week 5: 100 mg daily (in 1-2 divided doses)
• Week 6: 200 mg daily (in 2 divided doses)
• Week 7+: Increase by 100 mg weekly as needed

Maintenance Dosage

• Typical range: 300-500 mg/day in 2 divided doses
• Maximum: 700 mg/day in severe cases

Status Epilepticus Loading Dose

• 6.5 mg/kg single oral load if patient has been on lamotrigine for >6 months without history of rash 1
• Only use if patient has been off lamotrigine for <5 days

Dosing for Bipolar Disorder

Initial Titration Schedule

• Week 1-2: 25 mg once daily
• Week 3-4: 50 mg once daily
• Week 5: 100 mg daily
• Week 6+: Increase by 50 mg weekly as needed

Maintenance Dosage

• Target dose: 200 mg daily 2, 3
• Range: 50-300 mg daily based on response 4

Special Considerations

Drug Interactions

• When co-administered with valproate:

  • Reduce initial dose to 25 mg every other day
  • Slower titration: increase by 25-50 mg every 2 weeks
  • Lower maintenance dose (typically 100-150 mg/day)

• When co-administered with enzyme-inducing drugs (carbamazepine, phenytoin, phenobarbital):

  • Double the standard initial dose (50 mg/day)
  • Faster titration may be needed
  • Higher maintenance dose may be required (up to 400 mg/day)

Safety Precautions

1. Rash monitoring: The most serious adverse effect is Stevens-Johnson syndrome

   • Incidence of serious rash: 0.1% in bipolar studies 3, 5
   • Slow titration is essential to minimize risk
   • Discontinue immediately if rash appears

2. Common side effects:

   • Headache, nausea, infection, insomnia 3, 5
   • Generally well-tolerated compared to other mood stabilizers

3. Advantages over other mood stabilizers:

   • No weight gain
   • No need for blood level monitoring 3, 5
   • Lower incidence of diarrhea and tremor compared to lithium

Clinical Efficacy

• Bipolar disorder: Most effective for preventing depressive episodes rather than manic episodes 3, 5, 6
• Epilepsy: Effective for both partial seizures and generalized seizures 7

Monitoring Requirements

Unlike lithium or valproate, lamotrigine does not require:

• Regular blood level monitoring
• Liver function tests
• Complete blood count monitoring

The primary monitoring concern is vigilance for rash development, particularly during the titration period.

Common Pitfalls to Avoid

1. Titrating too quickly: This significantly increases rash risk
2. Failing to adjust dose with concomitant medications: Especially important with valproate (reduces lamotrigine clearance) and enzyme-inducing drugs (increase clearance)
3. Restarting at full dose after discontinuation: Always re-titrate if off medication for >5 days
4. Overlooking drug interactions: Particularly with oral contraceptives (may decrease effectiveness)

Lamotrigine has demonstrated particular benefit in women and elderly patients with epilepsy 7, and is especially valuable in bipolar depression where other mood stabilizers may be less effective 3, 5, 6.