OBJECTIVES: Antimicrobial agents are responsible for approximately one-quarter of the drug costs in hospitals. Since parenteral antibiotics are more expensive than oral antibiotics and are also associated with higher administration costs, the route and method of administration of antibiotics largely determine the total costs of antimicrobial treatment. The long term effectiveness of intravenous (IV) push administration of antibiotics in combination with an early switch from parenteral to oral antibiotics, within a ward-pharmacy organized program with the goal to reduce costs of antimicrobial treatment, was evaluated from the hospital perspective. METHODS: Ward Pharmacy Controlled (WPC) administration of antibiotics was introduced on a 40 bed internal medicine ward in a 700-bed teaching hospital. The costs of administration and utilization of parenteral and oral antibiotics included in the program were compared before (1997 to 1999) and after (2000 to 2004) implementation of WPC administration of antibiotics. RESULTS: Excluding 2004, WPC reduced utilization of parenteral antibiotics by 29%, from 3311±690 to 2345±377 DDD annually (p = 0.048). Also, the percentage of parenteral antibiotics to the total DDDs of antibiotics decreased from 63±5% to 53±4% (p = 0.035). Including 2004, with an exceptional high utilization of intravenous amoxicillin/clavulanic acid, the administration of parenteral antibiotics was reduced to 2507±430 DDD on average annually (p = 0.084) with a percentage to total of administered antibiotics of 55±6% (p = 0.11). The reduction of parenteral administration of antibiotics resulted in annual cost-savings ranging from EUR 14,278 up to 17,881. Administering parenteral antibiotics if possible by IV-push showed extra cost-savings ranging €3957 up to €8440 annually for the internal medicine ward. For a 700-bed teaching hospital the total cost-savings of WPC administration antibiotics amounted to at least €50,000 annually. CONCLUSIONS: WPC administration of antibiotics is effective in controlling and reducing costs of antimicrobial treatment.