Abstract
Background: Epilepsy is a common neurological disorder which demands long-term therapy and thereby carries a huge medical, social, psychological, and economic impact on a developing country. In India, it is estimated that 6-10 million people suffer from epilepsy which accounts for 1/5th of the global epilepsy burden. About 2/3rd of the newly diagnosed epilepsies are focal. The overall aim of treating epilepsy should be complete control of seizures, without causing any untoward reaction due to the antiepileptic therapy.

Aims and Objectives: The primary objectives are to analyze the pattern of antiepileptic drugs (AEDs) used in focal epilepsy and to assess the retention rate (success rate) at 1-year follow-up. The secondary objectives are to evaluate the effectiveness of substitution versus add-on in treatment failure cases and to assess the profile of adverse drug reactions (ADRs) reported.

Materials and Methods: This is a retrospective cohort study spanning from January 2009 to January 2014. Patients diagnosed as focal epilepsy attending Neurology outpatient department attached to BMCRI were included in the study. Data were collected through the integration of case records to retrieve the information regarding the demographic and clinical details, AEDs, and ADRs. Retention rate with initial AED was determined at the end of 1-year follow-up. Efficacy was assessed in terms of adequate seizure control between substitution and add-on therapies in all treatment failure cases. The results were analyzed by descriptive statistics, Chi-square, and Fisher’s exact tests.

Results: Out of 134 patients, 57% were males and 43% were females. The age ranged from 14 to 82 years. Monotherapy accounted for 67% of the total epileptic patients, in which 42% continued with initial, 25% substituted to alternative AED, and 33% of them required add-on therapy. The most common AEDs prescribed as monotherapy were carbamazepine (35.07%) and phenytoin (11.94%) and as add-on were carbamazepine with valproate (4.47%) and carbamazepine with phenytoin (4.47%). Carbamazepine showed higher retention rate among all initial AEDs at the end of 1-year follow-up (odds ratio: 2.1, 95% confidence interval: 1.03-4.24). On Fisher’s exact test, substitution therapy was better than add-on in adequate seizure control (P = 0.026). The overall incidence of ADRs was 21.6%. Drowsiness and agitation and tiredness were the common ADRs reported.

Conclusion: Despite the availability of newer AEDs, the domain of pharmacotherapy in focal epilepsy is still dominated by conventional AEDs. Carbamazepine has showed better retention rate at 1-year follow-up. Our study suggests that substitution therapy is a better alternative than add-on therapy in all treatment failure cases with initial AEDs.

Key words: Focal Epilepsy; Antiepileptic Drugs; Monotherapy; Substitution; Add-on; ADRs