Prescribing 350mg Lamotrigine Extended-Release
Combine 300mg and 50mg lamotrigine extended-release tablets to achieve the 350mg daily dose, as lamotrigine ER is available in 25mg, 50mg, 100mg, 200mg, 250mg, and 300mg tablet strengths. 1
Available Formulations
Lamotrigine extended-release tablets are FDA-approved and commercially available in the following strengths 1:
- 25mg
- 50mg
- 100mg
- 200mg
- 250mg
- 300mg
Practical Prescribing Strategy
To prescribe 350mg daily, write for:
- One 300mg tablet PLUS one 50mg tablet, taken together once daily 1
Alternative option:
- One 250mg tablet PLUS one 100mg tablet, taken together once daily 1
The first combination (300mg + 50mg) is preferable as it minimizes pill burden while achieving the exact target dose.
Important Administration Considerations
Extended-release tablets must be swallowed whole and should not be chewed, crushed, or broken, as this would destroy the extended-release mechanism and potentially cause peak toxicity 2. The extended-release formulation is specifically designed to reduce peak-to-trough fluctuations in serum levels, which can improve both seizure control and tolerability compared to immediate-release formulations 3.
Clinical Rationale for Extended-Release Formulation
Extended-release lamotrigine provides more stable serum concentrations throughout the dosing interval 3. In a study of patients converted from immediate-release to extended-release lamotrigine, 47% experienced greater than 50% reduction in seizure frequency, with a median 46% overall reduction in seizure frequency 3. The extended-release formulation achieves lower peak levels (reducing adverse effects like dizziness and diplopia) while maintaining higher trough levels (improving seizure threshold) 3.
Prescription Writing
Write the prescription as:
- Lamotrigine ER 300mg tablets: Take 1 tablet by mouth once daily
- Lamotrigine ER 50mg tablets: Take 1 tablet by mouth once daily
- Total daily dose: 350mg
Specify that both tablets should be taken at the same time each day, swallowed whole with water 2.