Abstracts

Rationale: Rationale: Lacosamide is an antiepileptic drug (AED) was approved in 2008 for the adjunctive use in patients with epilepsy >16 years. The purpose of this study was to study and demonstrate methods for surveillance of lacosamide in patients with epilepsy in Norway with focus on patient and population aspects.Methods: Methods: Data from routine TDM-service and additional data from the medical database at the National Center for Epilepsy regarding serum concentration measurements and clinical use of lacosamide, 2012-14, were utilized. All included samples were drug-fasting at assumed steady-state. Population-based data from the Norwegian Prescription Database (NorPD) was utilized to investigate the use of lacosamide in the country as a whole, 2010-14. The Regional Ethics Committee and National Institute of Public Health approved the study.Results: In total, 219 patients were included; 117 women/102 men, average age 53 years (range 4-86 years). The mean dose and concentration of lacosamide was 307 mg and 15.8 µmol/L (range 8.1-68.8). Mean C/D-ratio was 0.007 (range 0.016-0.82) µmol/L/mg, which demonstrates a 50-fold variability. The clinical use of lacosamide at the National Center reflected 154 patients (90 men/64 women), average age 36 years (range 4-78 years). All of the patients had a refractory epilepsy and used it as add on therapy (1- 4 other AEDs). 112 of the patients had a focal epilepsy, 16 had a multifocal epilepsy, 8 generalized epilepsy and 18 were not classified. Data from NorPD showed that use of lacosamide increased from 0.01 to 0.07 DDD/1000 inhabitants/day and 122 to 500 patients from approval to 2014. Limited off-label use in children <16 years was seen, 11-20 patients (2009-2014), consisting of 9% and 4%, respectively, of the patients.Conclusions: Conclusions: The present results demonstrate extensive pharmacokinetic variability of lacosamide, elucidating a need for individualization of therapy. The number of patients using lacosamide has increased every year. The use of complementary data sources elucidates how clinical use of AEDs contributes to pharmacovigilance in Norway.