The modifications of the medicinal treatments secondary to the hospitalizations have multiple reasons: reassessment of the previous treatment (conciliation), new therapeutic necessities, potential risk of iatrogeny or of drug interaction, restrictions of the therapeutic booklet, classification in reserve or hospital prescription ... These modifications are potentially generating extra costs for the Health Insurance and are monitored under the terms of the Contract of Good Use. The aims of this analysis are to define the medical-pharmaceutical rationale of the treatment changes imposed by hospitalization in a university-hospital center, their influence on the security of the medical treatment of patients and their financial implications for healthcare organizations