Financial impact of an aminoglycoside substitution program

In recent years, efforts toward cost containment have been emphasized in order to reduce health care costs. One area to be examined for cost containment is the field of antibiotics because of their escalating costs and the degree of inappropriate use. In June of 1985, an aminoglycoside substitution program was initiated wherein gentamicin was automatically substituted for tobramycin unless the physician specifically stated otherwise. Specific guidelines for tobramycin use were not established. The purpose of the study was to develop guidelines for the appropriate use of tobramycin and to determine the cost savings of the substitution program. A list was prepared of all patients who had received either gentamicin or tobramycin between July 1, 1985 and December 31, 1985. The health records of every fourth patient receiving gentamicin and all patients receiving tobramycin were retrospectively reviewed in depth. The remainder of the gentamicin cases were given a cursory review for substitutions from written tobramycin orders. Costs for both drugs were calculated from pharmacy drug acquisition records. Nine courses of tobramycin and 390 courses of gentamicin were found. Thirty-two gentamicin courses were substituted for tobramycin. Cost savings for the substituted gentamicin was approximately $1200 (45%). Additional savings would have been realized had four tobramycin courses been changed to gentamicin when culture and sensitivity results were reported. The cost of instituting the substitution was negligible. Guidelines for appropriate tobramycin use are presented.