Adjunctive therapy in epilepsy: a cost-effectiveness comparison of two AEDs

The objective of this study was to compare the relative cost-effectiveness of two AEDs by a prospective clinical audit. Patients starting on the adjun ctive therapies lamotrigine and topiramate were recruited from the out-pati ent epilepsy clinics at Queen Square. Three interview were scheduled: basel ine, three months follow-up and six months from baseline. Of the 81 patient s recruited, a total of 73 patients completed all three interviews. An inte ntion to treat analysis was performed on the data. Seizure severity and fre quency were assessed using the National Hospital Seizure Severity Scale. Si de-effects, adverse events and reasons for stopping medication were also re corded. At the third interview, a total of 47/73 (64%) were still on the prescribed adjunctive drug. Outcome was assessed by two methods: the >50% seizure red uction cited in the literature and a more stringent assessment of patient ' satisfaction' which we defined operationally on clinical criteria. Using th is definition, a total of 10/73 (14%) patients were 'satisfied'. The relati ve costs of starting patients on each of the two AEDs were: calculated, bot h drug costs and the costs of adverse events (the latter were defined as ev ents requiring urgent medical attention). The costs of the two drugs were c ompared. A number of methodological issues relating to cost comparison are discussed. Outcome and pharmaco-economic studies need to assess more than r eduction in number of seizures. They should take into account variables imp ortant for quality of life including side-effects and adverse events.