Antiepileptic drugs (AEDs) are relatively cheap but high volumes of prescriptions mean that substantial drug-budget savings may be possible by switching from innovator brands to cheaper generic drugs. Such savings have been achieved in many other treatment areas. However, more caution may be needed in the case of epilepsy because of the narrow therapeutic range of most AEDs; clinical principles of prescribing, which include making only cautious and gradual changes to dosing; the health and socioeconomic impact of breakthrough seizures or toxicity; and the need for long-term consistency of supply. Many physicians and patient groups are insufficiently reassured by current definitions of similarity between generics and innovator brands. Switching to the cheapest generic AED may offer drug-budget savings that outweigh any risk to patient safety. But to date, this cost-benefit analysis has not been done. We propose that all changes to established principles of treating epilepsy are evidence based and that the risks of switching are clearly defined.