This study evaluates drug cost outcomes related to automatic therapeutic substitution of branded tobramycin solution for inhalation (TOBI(®)) with inhaled generic preservative-free intravenous tobramycin (PFIT). A retrospective single-center evaluation of inhaled tobramycin use from 2008 through 2012 was performed. Number of doses dispensed and acquisition costs were obtained. Hourly wage data was acquired, pharmacy production costs were estimated and total cost-savings calculated. Days of therapy (DOTs) were determined for each year. Quality assurance and safety data was collected. In 2008, TOBI(®) drug costs and doses dispensed were $118,665 and 1769, respectively. Following implementation of the interchange in May 2009, TOBI(®) utilization ceased. PFIT costs in 2010 through 2012 averaged $34,775 annually and TOBI(®) cost-avoidance exceeded $94,000 annually when accounting for pharmacy production costs, which were determined to be at most $5.28 per dose. The maximum estimated pharmacy production cost ranged from $8812 to $11,299 annually. PFIT doses dispensed exceeded 1650 each year and annual DOTs ranged from 815 to 1069. The 40-month savings were calculated to be $374,706. Quality assurance and safety data identified one patient who refused PFIT due to odor complaints and one patient who was inappropriately administered a dose orally. Therapeutic substitution of TOBI(®) with PFIT can produce immediate and sustained savings with an acceptable safety profile.
Keywords: inhaled antibiotics; pharmacotherapy; pharmacy.