OBJECTIVES: This study aimed to analyse the pattern of prescription and use of antiepileptic drugs (AEDs), being its main focuses the characterization of off-label use and its costs. METHODS: Cross sectional survey, carried out from Sept. 2009 to Feb. 2010 in 20 pharmacies of Lisbon Region. Inclusion criteria:pharmacy users with a prescription including at least 1 AED (all medicines listed under the Anatomical Therapeutic Chemical code N03-Antiepileptics, having epilepsy in the SPC as main indication). Information was collected by interview, conducted by trained pharmacy students based on self-reported data. Prescription expenditures were obtained by crossing the official price of each medicine single unit, at the time of the study, with data on posology reported by each patient. Aggregate annual expenditures were calculated based on that information. RESULTS: Data from 543 patients was analyzed (61.3% females), age range 2-91 years (mean: 50.9). The main consumed AEDs were valproic acid (18.0%), pregabalin (16.2%), topiramate (15.7%) and carbamazepine (14.7%). The first prescriber was in 36.1% of the cases a neurologist and in 31.9% a psychiatrist. Epilepsy was the indication in 29.5% of the patients. Off-label use was found in 33.1% of the sample. Among the off-label sample, topiramate (28.2%), clonazepam (17.2%), valproic acid (16.7%) and gabapentine (10.9%) were the anticonvulsants most widely used off-label. Clonazepam (85.7%) and topiramate (59.0%) had most of their uses in off-label indications. Psychiatrists (59.2%) were the prescribers in the majority of the off-label cases. The main off-label indications were depression (31.4%) and mood stabilization (19.4%). Total costs with AEDs were 210,851.57€ in which 48,424.04€ (23.0%) represents an off-label cost. CONCLUSIONS: Approximately 1/3 of the sample used AEDs in off-label indications. Extrapolating to national data, it is estimated that more than €14 billion were paid for AEDs in off-label use (more than €13 billion paid by the NHS).