[Prophylactic treatment of mood disorders: cost effectiveness analysis comparing lithium and carbamazepine]

Economic impact of lithium therapy has seldom been assessed, economic comparisons with alternative mood stabilizers are almost non existent. This economic evaluation of preventive treatment of mood disorders recurrences (whether unipolar or bipolar) compared lithium with carbamazepine, through data from a randomized controlled clinical trial. A retrospective analysis of medical files of index patients is included in this trial, with experts' global ratings. A brief survey checked for representativity of in-patients length of stay. The model compared two cohorts of patients followed-up for two years after prophylactic treatment had begun. Rates of recurrence and direct medical costs related to mood disorders (prophylactic treatment, treatment of recurrences and serious adverse effects) were assessed. Data extrapolation was necessary because of variable lengths of follow-up during the trial and was based on medical review of index patients. Assessment of consumed health care resources were derived from the available database of the clinical trial, when necessary practice guidelines and experts' opinions were added to the model. Costs were valued according to available french unit costs (Vidal, NGAP, and Comptes de la santé). Analysis only included direct costs. An estimate of mean cost of care of 15,404 French francs per year per patient was calculated. The components of health costs show that in-patient costs are the most important part of annual medical costs for mood disorders (70% of the total costs). Prophylactic medication costs accounted for only 6.9% of total costs. Comparison of prophylactic alternatives gave lithium a clinical benefit with 27% fewer recurrences than carbamazepine. Lithium led to an economic benefit of 4,280 French francs per year of treatment for a single patient. Robustness of this finding was assessed through a sensitivity analysis on estimate of length of stay. Total costs of treatment would be equal between lithium and carbamazepine if length of stay in hospital for lithium patients was increased by 51%. According to the cost-effectiveness analysis developed in this study, lithium should stay the "gold standard" of prophylactic treatment of recurrent mood disorders, and has both clinical and economic advantages compared to carbamazepine.