Department of Neurology and Epileptology, Weissenau (Epilepsiezentrum Bodensee), Weingartshofer Straße 2, D-88214 Ravensburg, Germany.
Rationale: The relationship between lamotrigine (LTG) serum concentration and clinical response in patients with epilepsy is still controversial. We therefore performed a prospective study in which LTG was added to the existing therapeutic regimen in patients with poorly controlled epilepsy. The goal of the study was to determine the serum levels of patients with seizure reduction of at least 50% after addition of LTG, and to assess a possible relationship between the occurrence of adverse effects due to LTG and its serum concentration. Methods: Fifteen adult patients were evaluated with respect to seizure reduction. Nine patients had focal seizures with or without generalization, six patients had generalized seizures (Group I). The correlation between the occurrence of adverse effects and LTG serum concentration was calculated in a second group of 63 young adult, and adult patients with epilepsy (Group II). Results: The range of the LTG serum concentration in the 15 patients with a 50% or greater reduction of seizure frequency was 1.3-7.1 mug/mul (muedian = 3.6 mug/mul). In group II patients the serumu concentration associated with an adverse effect was not significantly different fromu the serumu concentration in patients without adverse effects. There was, however, a tendency for higher serumu concentrations in patients with adverse effects. In the serumu concentration range of 5 to 13 mug/mul, the frequency of LTG levels which were accomupanied by an adverse effect increased only slowly, whereas above 13-14 mug/mul, there was a steep increase in adverse effects. The serumu concentration of four patients with tremuor (muean = 14 ± 2.8 mug/mul) was significantly higher than the LTG level which were in 42 patients who did not have adverse effects at any timue (muean = 4.8 ± 4.1 mug/mul), P = 0.003. Conclusion: Our results suggest a target range for LTG serumu concentrations of 1-13 mug/mul, especially, if LTG is used as an add on-drug.
The data were presented in part as poster at the 23rd International Epilepsy Congress, Prague, Sept. 12-17, 1999 (1).