Cognitive effects of lamotrigine compared with topiramate in patients with epilepsy

Objective: To compare the cognitive effects of lamotrigine vs topiramate as adjunctive therapy in adults with epilepsy. Methods: A multicenter, double-blind, randomized, prospective study was conducted in adults with partial seizures. Lamotrigine or topiramate was introduced as an adjunctive therapy to carbamazepine or phenytoin and titrated over 8 weeks to target doses. These drugs were maintained another 8 weeks ( maintenance phase) without dosage changes. The primary endpoint was change from screening to the end of the maintenance phase in a combined analysis of standardized measures of cognition ( Controlled Oral Word Association Task [COWA]; Stroop Color - Word Interference; Digit Cancellation; Lafayette Grooved Pegboard, dominant hand; Rey Auditory Verbal Learning Test, delayed recall; and Symbol - Digit Modalities test). Results: For the primary endpoint, cognitive performance at the end of the maintenance phase was better with lamotrigine than with topiramate (415.3 vs 315.1; p < 0.001). On the individual cognitive tests, performance was better with lamotrigine than with topiramate in mean changes from screening on the COWA ( p < 0.001), Stroop Color - Word Interference (p < 0.038), and Symbol - Digit Modalities tests ( p < 0.001). The treatment effect exceeded the minimum clinically important difference for the COWA and the Symbol - Digit Modalities test. Mean changes from screening in the Performance-On-Line test simulating driving skills reflected better performance with lamotrigine than with topiramate ( p = 0.021). The median percentage change from baseline in seizure frequency was lower with lamotrigine than with topiramate during the escalation phase ( - 80% vs - 100%; p = 0.028) but not during the maintenance phase ( - 75% vs - 100%; p = 0.062). The frequencies of cognitive adverse events and of premature withdrawals related to cognitive decline were higher with topiramate than with lamotrigine ( 6% vs 0%; p = 0.013). Conclusion: Lamotrigine had significantly less impact than topiramate on measures of cognition when used as adjunctive therapy for partial seizures.