Recommended Dosage and Usage of Lamotrigine for Epilepsy and Bipolar Disorder
For epilepsy, lamotrigine should be started at 25 mg once 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 an effective maintenance dose of 300-500 mg daily (divided twice daily); 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, then increase by 50 mg weekly until reaching a maintenance dose of 200 mg daily.
Dosing for Epilepsy
Initial Titration
- Week 1-2: 25 mg once daily
- Week 3-4: 50 mg once daily
- Week 5: 100 mg once daily (or 50 mg twice daily)
- Week 6+: Increase by 100 mg weekly as needed
Maintenance Dosing
- Adults: 300-500 mg/day divided twice daily
- Children (2-12 years): 5-15 mg/kg/day divided twice daily (maximum 400 mg/day) 1
- For patients with refractory seizures, doses up to 700 mg/day may be considered
Special Considerations for Epilepsy
- For patients taking valproate: Reduce initial and maintenance doses by 50% due to drug interaction
- For patients taking enzyme-inducing antiepileptic drugs (carbamazepine, phenytoin): May need higher maintenance doses
- Loading dose for patients who missed medication: 6.5 mg/kg single oral load if on lamotrigine for >6 months without history of rash and off lamotrigine for <5 days 1
Dosing for Bipolar Disorder
Initial Titration
- Week 1-2: 25 mg once daily
- Week 3-4: 50 mg once daily
- Week 5: 100 mg once daily
- Week 6+: Increase by 50 mg weekly as needed
Maintenance Dosing
- Standard target dose: 200 mg daily 2, 3
- Effective dose range: 50-300 mg daily 4
- Continue for at least 2 years after the last mood episode 2
Special Considerations for Bipolar Disorder
- When used with valproate: Reduce initial and target doses by 50%
- When used with carbamazepine: May need to increase target dose
- Lamotrigine is particularly effective for preventing depressive episodes 3
Safety and Monitoring
Rash Precautions
- Serious rash (including Stevens-Johnson syndrome) occurs in approximately 0.1% of patients 3
- Risk of serious rash can be minimized through slow titration
- Do not load if patient has history of rash or if not previously on lamotrigine 1
- Discontinue immediately if rash appears, especially if accompanied by fever, lymphadenopathy, or facial swelling
Drug Interactions
- Valproate increases lamotrigine levels: Reduce lamotrigine dose by 50%
- Carbamazepine, phenytoin, and other enzyme inducers decrease lamotrigine levels: May need higher doses
- Oral contraceptives may decrease lamotrigine levels
Monitoring Parameters
- Baseline: Complete blood count, liver function, renal function
- Regular monitoring: Serum levels not routinely required but may be helpful in certain situations
- Watch for signs of rash, especially during the first 8 weeks of treatment
- Monitor for suicidal ideation, particularly when initiating therapy
Clinical Pearls
- Lamotrigine is considered one of the safest mood stabilizers due to its favorable side effect profile 2
- Unlike many other mood stabilizers and antipsychotics, lamotrigine does not appear to cause weight gain 3
- For bipolar disorder, lamotrigine is most effective for preventing depressive episodes rather than manic episodes 3
- For epilepsy, lamotrigine is effective against both partial and generalized seizures 5
- Common side effects include headache, nausea, dizziness, somnolence, and diplopia 3, 5
- Slow titration is critical to minimize risk of serious rash
Lamotrigine has demonstrated efficacy in both epilepsy and bipolar disorder with a generally favorable side effect profile compared to other options. The key to safe use is proper titration, especially when initiating therapy.