Up until now, the optimal dose of lamotrigine, when given as monotherapy, had yet to be determined. The study, conducted using retrospective data from two epilepsy medical centers in Israel, included a total of 188 patients. They evaluated dosage and treatment efficacy as well as adverse effects and retention rate.
The researchers found significant statistical connections between the lamotrigine dosage efficacy and the patient’s age and duration of epilepsy. A total of 46.2% of the patients who had epilepsy for ≥5 years required a higher lamotrigine dose of >250mg daily to control their seizures, while just 35.7% of those with a disease duration of <5 years needed the same level of dosing.
Similarly, for patients aged >30 years old, a higher lamotrigine dose was needed to control their seizures. Fifty-two percent of 31 to 50 year-olds and 53.8% of those >50 years old needed a lamotrigine dose of >250mg daily to control their seizures. Of the 18 to 30 year-olds, just 27.9% required a dosage of >250mg daily.
The authors noted a good level of tolerability for lamotrigine as a monotherapy, with 68% of the patients in the study sample continuing treatment for at least 1 year of follow-up with good efficacy and minor side effects.
A reason for the older participants needing a higher dosage could have been due to changes in metabolism, the authors explained. However, the fact that this high dosage was also needed in 31 to 50 year-old group suggests this is not the only reason.
Overall, the major factors that impact the dosage efficacy of lamotrigine were patient’s age and duration of disease. Due to the statistical significance in difference of efficacy, the authors suggest that certain subgroups of adult epilepsy patients who will be treated with lamotrigine as monotherapy should initiate their doses at 250mg daily or higher.