Lamotrigine Dosing for Adults with Epilepsy or Bipolar Disorder
For adults with epilepsy or bipolar disorder, lamotrigine should be initiated at a low dose and gradually titrated to the target dose of 200-400 mg/day for epilepsy and 200 mg/day for bipolar disorder, with adjustments based on concomitant medications. 1, 2, 3
Dosing for Epilepsy
Initial Titration Schedule
- Start with 25 mg once daily for 2 weeks, then increase to 50 mg once daily for 2 weeks 1, 4
- After 4 weeks, can increase by 50 mg every 1-2 weeks until reaching maintenance dose 4, 5
- Target maintenance dose: 200-400 mg/day (divided into two doses) 1, 4
Special Considerations for Epilepsy
- For patients on enzyme-inducing medications (e.g., carbamazepine, phenytoin): target dose may need to be increased to 600 mg/day 1, 5
- For patients on valproate: reduce initial and maintenance doses by 50% due to reduced clearance of lamotrigine 1, 4
- Oral loading of 6.5 mg/kg may be considered only for patients previously on lamotrigine for >6 months without history of rash and off medication for <5 days 1
Dosing for Bipolar Disorder
Initial Titration Schedule
- Start with 25 mg once daily for 2 weeks 2, 3
- Increase to 50 mg once daily for weeks 3-4 2, 3
- Increase to 100 mg once daily for week 5 2, 3
- Increase to 200 mg once daily for week 6 and beyond (maintenance dose) 2, 3
Special Considerations for Bipolar Disorder
- Lower serum concentrations may be effective for bipolar disorder compared to epilepsy, with therapeutic benefit observed at mean concentrations of 3,341 ng/mL 6
- Maintenance dose range: 50-300 mg/day, with most patients responding to 200 mg/day 2, 3
- Slow titration is essential to minimize risk of serious rash 3
Medication Interactions and Dose Adjustments
- When co-administered with valproate: reduce lamotrigine initial and target doses by 50% 1, 3
- When co-administered with enzyme-inducing antiepileptics (carbamazepine, phenytoin): increase lamotrigine target dose by 50-100% 1, 5
- Dose adjustments should be made when adding or removing interacting medications 1, 5
Safety Considerations
- Slow titration is critical to minimize risk of serious rash, including Stevens-Johnson syndrome 4, 3
- Risk of rash is approximately 10% overall, with serious rash occurring in 0.1% of patients with bipolar disorder 3
- Do not exceed recommended initial doses or titration rates 4, 3
- Extended-release formulations are available in 25,50,100,200,250, and 300 mg tablets 7
- Lamotrigine is generally well-tolerated with common side effects including headache, nausea, dizziness, and insomnia 3