Clinical and biological assessment of lamotrigine and levetiracetam plasma assays at the Rennes University Hospital

Abstract : Introduction: Requests for lamotrigine and levetiracetam plasma assays have increased significantly since their development in the biological and forensic toxicology laboratory at the University Hospital of Rennes in 2015. The purpose of this study was to evaluate the follow-up of French National Authority for Health (HAS) guidelines for antiepileptic drug assays and the impact of assay results on medical management.Methods: Two hundred and forty-two assay results of these two antiepileptics for 169 patients hospitalized in different care wards between 2015 and 2018 were retrospectively analyzed.Results: The mean age of the study population was 50.3±25.4 years. Of the 207 assays prescribed for epilepsy, 177 (85.5%) were in line with the 2007 HAS guidelines, namely: 76/177 (42.9%) for therapeutic adjustment in the event of seizure recurrence or aggravation; 45/177 (25.4%) for specific clinical situations; 23/177 (13%) for proven or suspected poor compliance; 23/177 (13%) for suspected overdose; 8/177 (4.5%) following initiation of treatment; and 2/177 (1.1%) for drug interaction management. Thirty of the 207 assays (14.5%) were thus inappropriate. No significant differences were found regarding the hospitalization frequency after a visit to the emergency room (P=0.9) between patients with lamotrigine and/or levetiracetam plasma assays in therapeutic ranges versus those with concentrations outside the therapeutic ranges. Dosage changes were more frequent in patients with assays in therapeutic ranges compared to patients with plasma assays outside the therapeutic ranges (P=0.0015), suggesting a treatment reassessment primarily based on clinical criteria.Conclusion: The analysis of requests for antiepileptic drug assays at the University Hospital of Rennes revealed that clinicians were well aware of the HAS guidelines. In addition, the assay results were mainly consistent with clinical intuition, suggesting a real added value for patient management. However, the consequences in terms of changes in medical care seem limited. This assessment illustrates the importance of strengthening the dialogue between pharmacists, biologists and clinicians.