Purpose: Pharmacokinetics of antiepileptic drugs (AEDs) can be altered by age-related changes in physiology, thereby altering clinical effects, especially tolerability, in older adults. We compared two dosages of topiramate (TPM) in a pilot study of patients >or=60 years of age with partial-onset seizures.
Methods: In this 24-week, double-blind, randomized, parallel-group study, patients with one or more seizures in previous 6 months were randomized to treatment with 50 or 200 mg/day TPM. TPM was initiated as monotherapy or added to one AED and titrated by 25 mg/day per week to target or maximum tolerated dose as the concomitant AED, if any, was withdrawn.
Results: Thirty-eight patients were randomized to the 50 mg/day TPM (mean age, 68 years) and 39-200 mg/day TPM (69 years). Seizure control was similar with the two dosages when TPM could be used as monotherapy, whereas 200 mg TPM was more effective than 50 mg in patients requiring adjunctive therapy. The overall incidence of adverse events was similar for the two dosages--66% with 50 mg and 62% with 200 mg TPM. Most common adverse events were somnolence (TPM 50, 13%; TPM 200, 8%), dizziness (13% vs. 8%), and headache (13% vs. 5%). Of 10 (13%) patients reporting a cognitive-related adverse event, six patients were assigned to the 50-mg group. A total of 14 patients (18%; seven in each group) discontinued TPM due to adverse events.
Conclusions: This pilot study supports the practice of using low-to-moderate dosages of AEDs in older adults.