Cost savings associated with use of gentamicin versus tobramycin

A hospital's use and costs of tobramycin sulfate versus gentamicin sulfate before and after a tobramycin use review were compared. Retrospective audits of 100 charts of adult patients in a 515-bed hospital were performed for two six-month periods in 1983-84. Tobramycin use was considered appropriate in patients with serum creatinine concentrations greater than 1.5 mg/dL or pre-existing renal disease, in any patient over 70 years of age, and in patients with neutropenia, documented pseudomonas infection, or infection with an organism shown to be resistant to gentamicin but sensitive to tobramycin. Tobramycin use was not justifiable in 37 (18.7%) of 198 patients whose charts were evaluable. Use of gentamicin in these 37 patients would have saved $14,300. The infection control committee was notified of the audit results; the audit results and recommendations for tobramycin use were included in a letter to all physicians; and the infectious disease service held educational conferences on tobramycin use. In the first six months after the corrective measures, mean monthly tobramycin use decreased by 38% and gentamicin use increased by 48.9%. Total aminoglycoside costs decreased 30.2% and total aminoglycoside use decreased 12.5%. In the second six months after intervention, mean monthly tobramycin use was 11% less than before intervention, and mean monthly gentamicin use was 13% greater than before intervention. Total aminoglycoside costs were 3.6% less and total aminoglycoside use was 4% less than before the audit. The tobramycin use audit and subsequent interventions with prescribers were effective in reducing tobramycin use and costs for approximately six months; decreases in tobramycin use and costs were smaller during the second six months after intervention.