Adverse cognitive effects of antiepileptic pharmacotherapy: Each additional drug matters

The study was set up to evaluate the impact of the total drug load of antiepileptic pharmacotherapy on cognition. Retrospective analyses were based on 834 patients with epilepsy who underwent a brief routine assessment of executive function and verbal memory (EpiTrack Plus) at our department. The total drug load was quantified in two ways: (1) number of concurrent antiepileptic drugs (AEDs) and (2) total drug load according to the defined daily dose (DDD) provided by the World Health Organization. The cognitive measures showed higher inverse correlations with the number of AEDs (executive function: r=-0.35, p<0.001; memory: r=-0.22, p<0.001) than with the total DDD (executive function: r=-0.27, p<0.001; memory: r=-0.17, p<0.001). Reanalysis with statistical control for disease severity hardly changed the aforementioned results. With each additional drug in polytherapy, we observed a significantly lower performance in executive function. In this regard an additional explorative approach revealed that regimens combining AEDs with favorable cognitive profiles were associated with higher cognitive performance. Correlations between indicators of disease severity and drug load indices were low: altogether explaining only up to 9% of the observed variance in drug load. The findings demonstrate a considerable adverse effect of a higher drug load on cognition, especially on executive functions. Simply counting the number of drugs may be sufficient as a rough estimate of the risk of side effects. However, the combination of AEDs with favorable cognitive profiles may attenuate the negative effect of the total drug load.