Off-label use of inhaled tobramycin in Ontario, Canada

Inhaled tobramycin solution is indicated for use in the management of Pseudomonas aeruginosa in patients with cystic fibrosis (CF). Concerns have been raised regarding increasing off-label use of inhaled tobramycin, particularly for the management of COPD. We conducted an 8-year repeated cross-sectional study examining the indication for prescription claims for inhaled tobramycin in Ontario paid for by the Public Drug Benefit Program, which covers all Ontario residents with financial needs or aged 65 and older. Inhaled tobramycin prescription claims increased approximately 3 times greater from 86 prescriptions in the second quarter of 2007 to 261 prescriptions in the first quarter of 2015. Approximately half of all prescriptions (range: 46-65%) per quarter were dispensed to patients with CF. A large proportion of prescriptions (range: 31-36%) were dispensed to individuals who did not have a diagnosis of CF but had a diagnosis of COPD. In 2014, there were 324 unique users of inhaled tobramycin solution in the Ontario Public Drug Program (OPDP). Only half of users (54%; n=163) had a diagnosis of CF. Our study found increasing prescriptions of inhaled tobramycin from 2007 to 2015 in the OPDP with approximately half of these claims being for off-label use, mostly among patients with COPD.