Drug-resistant epilepsy and topiramate: Plasma concentration and frequency of epileptic seizures.

Topiramate (TPM) is a second-generation antiepileptic drug (AED), acting on drug-resistant epilepsy. The aim of the study was to evaluate the influence of the dose, use of other AEDs on TPM plasma concentration (Cp ), and frequency of epileptic seizures. A cross-sectional analytical study was developed with patients aged 18-60 years, for diagnosis of drug-resistant epilepsy, using TPM in monotherapy or associated with other AEDs. The following variables were analyzed: age, frequency of epileptic seizures, pharmacotherapeutic regimen with its respective doses, adherence to medication treatment, and adverse events score. Thirty-seven patients were included, 83.8% of the patients presented Cp below the therapeutic range. Multiple linear regression estimated that the increase of 1.0 mg/kg/d promoted an increase of 0.68 µg/mL in TPMCp , while the use of inducers predicted a reduction of 2.97 µg/mL (P < .001). Multiple Poisson regression predicts that an increase of 1.0 µg/mL in TPMCp decreased the patient's chance of presenting seizures, and patients using AED inducers were about ten times more likely to present seizures than those who do not use (P < .001). In addition, for patients using AED inducers with Cp below the therapeutic range, the mean number of seizures per month was greater than those with Cp within the therapeutic range. The prescribed dose and the use of AED inducers influence Cp of TPM, likewise the low Cp of first-line AEDs and of the adjuvant in the treatment, TPM, as well as low TPM dose seem to affect the control of epileptic seizures.