OBJECTIVES: To evaluate from the public payer point of view savings in the acute management of methanol or ethylene glycol poisoning when replacing ethanol by fomepizole as first line antidote therapy. METHODS: A decision tree model based on a expert consensus process was built, using DATA TM Tree Age 4.0, to predict the average additional costs per patient due to the treatment of side effects of each antidote in 8 situations (branches). The side effects were related to the following issues: depression of the central nervous system, pancreatitis, and hemodialysis complications. For each of the five countries (Belgium, France, Italy, Ireland, Norway) one senior expert in toxicology and intensive care provided: 1) An estimation of the probability of occurrence of each side effect, and 2) A value (real price) of each relevant treatment of each side effect. The costs were given as per-S2 2003 value. As the time frame of the study was the discharge of hospital, no discount rate was calculated. RESULTS: In each of the five countries, the cost of side effect management was cheaper in the "fomepizole" situation than in the "ethanol" situation. For methanol poisoning, the savings in the fomepizole group ranged from 724€ to 1 667 €, 22.3% to 88.7% in proportion. For ethylene-glycol poisoning the saving in the fomepizole group ranged from 251€ to 2847€, 26.3% to 76.9% in proportion. CONCLUSION: Fomepizole, when used as a first line antidote therapy represents a source of potential savings in the management of side effects: Up to 1667€ for methanol poisoning and up to 2847 € for ethylene glycol poisoning.