Does Percent Reduction In Seizure Frequency Correlate With Plasma Concentration Of Anticonvulsant Drugs? Experience With Four Anticonvulsant Drugs

Objective: To investigate the relationship between the percentage reduction in seizure frequency in patients with epilepsy and plasma concentrations after oral administration of 4 anticonvulsant drugs,Methods: Patients with a minimum of 25% reduction in their seizure frequency from their baseline value were declared responders. The percentage reduction in seizure frequency was plotted against plasma concentrations with use of pharmacodynamic models (Linear, log-linear, E-max, and sigmoidal E-max models). Zn addition to pharmacodynamic models, a logistic regression model was also fitted to the concentration-response data, with a value of 1 for responders and 0 for nonresponders,Results: The concentration-effect relationship could not be adequately described either by the pharmacodynamic models or by the logistic regression analysis.Conclusions: Based on the results obtained from both pharmacodynamic models and logistic regression analysis the percentage reduction in seizure frequency may not be a true surrogate marker for anticonvulsant drugs to establish a pharmacodynamic relationship with plasma concentrations.