Changing from brand name to generic antiepileptic drugs (AEDs) is increasingly being advocated by the authorities, principally for budgetary reasons. However, caution should be exercised since AEDs may have a narrow therapeutic margin, the regimen with AEDs may be complex, the consequences of uncontrolled seizures may be severe, and risk of side effects is relatively high, particularly when seizures are difficult to control. This article focuses on the possible problems that can arise from the substitution of AEDs formulations, such as loss of seizure control and emergence of new side effects. We would advise that patients stay on the same formulation of the first AED, whether a brand name or generic AED. Switching AED formulations should always be done with the necessary caution and under the physician's supervision. Closer follow-up during the transitional period is necessary, and dosage adjustment may be required. The patient should be given full and correct advice about risks involved in switching AED formulations.