Impact of a practical two-stage intervention on aminoglycoside usage.

To control aminoglycoside usage and costs, a two-stage intervention was implemented at this 1,000-bed, major Canadian teaching hospital. An informational stage, reviewing the therapeutic equivalence of netilmicin, gentamicin, and tobramycin in various internal publications, was followed by an automatic therapeutic interchange program. The intervention involved removing netilmicin from the formulary and substituting gentamicin for tobramycin. Comparing the 8-week pre-implementation period with the 24-week, post-implementation period, new orders for netilmicin declined from 42% to less than 1% of the total new aminoglycoside courses initiated. During the same time frame, new orders for gentamicin increased from 50% to 90%, orders for tobramycin remained stable at approximately 5.5%, and orders for amikacin remained unchanged at 1%. A retrospective health record review revealed a low incidence of microbiologically inappropriate interchanges. Pharmacy manpower requirements were minimal and prescriber acceptance was high. A +27,000 cost savings per year was estimated.