How do I convert a patient from Lamictal (lamotrigine) to Lamictal XR (extended-release lamotrigine)?

Converting from Lamictal to Lamictal XR

When converting a patient from immediate-release lamotrigine (Lamictal) to extended-release lamotrigine (Lamictal XR), use a 1:1 dose conversion with the entire daily dose given once daily, with no need for retitration.

Conversion Process

The conversion from immediate-release lamotrigine to extended-release lamotrigine follows these principles:

• Direct 1:1 conversion: The total daily dose of immediate-release lamotrigine can be directly converted to the same total daily dose of Lamictal XR 1
• Once-daily dosing: Lamictal XR is administered once daily, regardless of how many times per day the immediate-release formulation was being taken 2, 3
• No retitration needed: Unlike initial lamotrigine therapy, which requires slow titration to minimize rash risk, conversion between formulations does not require retitration 4

Clinical Benefits of Conversion

Converting to Lamictal XR offers several advantages:

• Improved seizure control: Studies show a 46% median reduction in seizure frequency when patients are converted from immediate-release to extended-release lamotrigine, with 47% of patients experiencing >50% reduction in seizure frequency 4
• Better tolerability: The extended-release formulation provides more stable serum drug concentrations with:
  • Lower peak levels that may reduce adverse effects such as dizziness, blurred vision, and unsteadiness
  • Higher trough levels that may improve seizure control 4, 5
• Enhanced adherence: Once-daily dosing simplifies the medication regimen and may improve medication adherence 2, 5

Practical Considerations

When implementing the conversion:

• Timing: The conversion can be done overnight with the first dose of Lamictal XR given the morning after the last dose of immediate-release lamotrigine
• Administration requirements: Lamictal XR tablets must be swallowed whole and should not be chewed, crushed, or divided 3
• Monitoring: While serum level monitoring is not routinely required during conversion, it may be helpful in certain situations, particularly when lamotrigine is used with medications that affect its metabolism (e.g., valproic acid, enzyme-inducing antiepileptics) 1
• Bioequivalence: Generic lamotrigine XR tablets have been demonstrated to be bioequivalent to the brand Lamictal XR in FDA studies 6

Potential Challenges and Solutions

• Dosage strength limitations: If the patient's current dose doesn't match available Lamictal XR strengths (25,50,100,200,250, and 300 mg tablets 7), the closest available strength should be used
• Initial adjustment period: Some patients may experience a change in side effect profile during the first few days after switching due to differences in the pharmacokinetic profile 4
• Missed doses: The impact of missed doses may be greater with once-daily dosing, so patient education about adherence is particularly important 2

Special Populations

• Patients on enzyme-inducing antiepileptics: No special adjustment is needed beyond the standard 1:1 conversion
• Patients on valproic acid: No special adjustment is needed beyond the standard 1:1 conversion, but monitoring may be beneficial as valproic acid inhibits lamotrigine metabolism 1

The conversion to Lamictal XR is straightforward and offers potential benefits in terms of seizure control, tolerability, and convenience for patients requiring long-term lamotrigine therapy.