Therapeutic drug monitoring of levetiracetam: Method validation using high-performance liquid chromatography-ultraviolet detector technique and usefulness in patient care setting.

Objectives: To develop and validate a modified HPLC-UV method for the estimation of serum levetiracetam levels and to assess the usefulness of serum levetiracetam estimation in epileptic patients.

Materials and methods: Modification of a previously existing HPLC-UV method was performed using liquid- liquid phase extraction and processing using reverse phase analytic HPLC-UV detector technique followed by method validation. Serum samples of patients attending our hospital's Therapeutic Drug Monitoring Outpatient Department services were analyzed for levetiracetam levels using the study method. Data of the past 6 years (2015-2020) were descriptively analyzed.

Results: The modified HPLC-UV method was validated as per ICH Q2 (R1) 2005 guidelines. Usefulness of levetiracetam estimation was assessed in 1383 patients (635 children, 683 adults, 40 elderly, and 25 pregnant women). Levetiracetam levels were within the therapeutic range (TR) in 520 children, 543 young adults, 35 elderly patients, and nine pregnant women. In 112 of 232 patients with low levetiracetam levels, poor compliance was elicited. Of 641 patients on polytherapy, 446 patients had levetiracetam values within TR, whereas 29 had values above and 166 patients had values less than TR. Sodium valproate, phenytoin sodium, and carbamazepine affected levetiracetam levels when given concomitantly. Levetiracetam dose was adjusted in 61 patients with abnormal levels for better clinical response. Good seizure control was noted in 913 (82.47%) patients whose levels were within TR, whereas 136 (58.62%) patients with low levels reported an increase in seizure frequency.

Conclusions: The modified HPLC-UV method is simple, rapid, efficient, and reliable for assaying serum levetiracetam.