Lamotrigine Dosage and Usage for Epilepsy and Bipolar Disorder
For epilepsy, lamotrigine should be started 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 200-400 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 increase by 50 mg weekly until reaching the maintenance dose of 200 mg daily.
Dosing for Epilepsy
Initial Titration Schedule
- Week 1-2: 25 mg once daily
- Week 3-4: 50 mg once daily
- Week 5: 100 mg daily (50 mg twice daily)
- Week 6: 200 mg daily (100 mg twice daily)
- Week 7+: Increase by 100 mg weekly as needed
Maintenance Dosage
- Typical range: 200-400 mg daily in divided doses
- Maximum dose: Up to 700 mg daily in some cases
Special Considerations for Epilepsy
- Loading dose option: 6.5 mg/kg single oral load if patient has been on lamotrigine for >6 months without history of rash and has been off medication for <5 days 1
- Do not load if patient has history of rash or was not previously on lamotrigine
- Therapeutic serum level for epilepsy: 3,000-14,000 ng/ml
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
- Recommended dose: 200 mg daily
- Range: 50-300 mg daily based on clinical response
- Lower therapeutic serum levels may be effective for bipolar disorder compared to epilepsy (mean effective concentration: 3,341±2,563 ng/ml) 2
Dose Adjustments Based on Concomitant Medications
With Valproate
- Start at 25 mg every other day for 2 weeks
- Then 25 mg daily for 2 weeks
- Then increase by 25-50 mg every 1-2 weeks
- Maintenance dose: typically 100-150 mg daily
With Enzyme-Inducing Antiepileptic Drugs (carbamazepine, phenytoin, phenobarbital)
- Start at 50 mg daily for 2 weeks
- Then 100 mg daily for 2 weeks
- Then increase by 100 mg every 1-2 weeks
- Maintenance dose: typically 300-500 mg daily
Clinical Efficacy
- For bipolar disorder: Most effective for prevention of depressive episodes 3, 4
- For epilepsy: Effective for both partial and generalized seizures 5
- Time to therapeutic effect: 6-8 weeks for full mood stabilization in bipolar disorder
Safety Considerations
Rash Monitoring
- Serious rash risk: approximately 0.1% in bipolar disorder studies 3
- Risk factors: rapid titration, concurrent valproate, history of drug allergy
- Most rashes occur within first 8 weeks of treatment
- Discontinue immediately if rash appears with fever, lymphadenopathy, facial swelling, or mucosal involvement
Common Side Effects
- Headache, nausea, dizziness, somnolence, diplopia
- Less common: insomnia, tremor, ataxia
- Advantage: Does not cause weight gain unlike many other mood stabilizers 3
Monitoring Parameters
- No routine blood level monitoring required (unlike lithium or valproate)
- Clinical response and tolerability are primary monitoring parameters
- Baseline and periodic assessment for rash
Practical Tips
- Slow titration is essential to minimize rash risk
- Evening dosing may help reduce daytime sedation
- Divided doses (twice daily) may improve tolerability for doses >200 mg
- Patient should be instructed to report any rash immediately
- If treatment is interrupted for more than 5 days, restart at initial titration schedule
Lamotrigine's favorable side effect profile makes it particularly beneficial for women and elderly patients with epilepsy 5, and its efficacy in preventing depressive episodes makes it valuable for bipolar disorder maintenance therapy.