Influence of age and comedication on steady-state clonazepam serum level-dose ratios in Japanese epileptic patients

Background: In antiepileptic drugs, the marked inter- and intrapatient vari ability of the level-dose ratio makes it difficult to predict serum concent rations from the administered per kg dose. It is therefore important to ide ntify factors, such as age and comedication, that could contribute to this observed variability. Objective: To investigate the effect of age and comedication on clonazepam (CZP) level-dose (L/D) ratios. Method: A retrospective evaluation of data from 137 epileptic patients who had received clonazepam. Results: The CZP L/D ratio increased slowly with age up to 15 years in pati ents on monotherapy. Associated antiepileptic therapy affected the CZP L/D ratio, which was significantly reduced in patients on polytherapy as compar ed to patients on monotherapy. Conclusion: The study therefore suggests that routine monitoring of CZP ser um levels is extremely useful, especially in the paediatric age group, and in patients who require associated antiepileptic medication.