BACKGROUND: Adherence with tobramycin inhalation solution (TIS) during routine cystic fibrosis (CF) care may differ from recommended guidelines and affect health care utilization.

METHODS: We analyzed 2001-2006 healthcare claims data from 45 large employers. Study subjects had diagnoses of CF and at least 1 prescription for TIS. We measured adherence as the number of TIS therapy cycles completed during the year. Interquartile ranges (IQR) were created for health care utilization and logistic regression analysis of hospitalization risk was conducted by TIS adherence categories.

RESULTS: Among 804 individuals identified with CF and a prescription for TIS, only 7% (n = 54) received 4 or more cycles of TIS per year. High adherence with TIS was associated with a decreased risk of hospitalization when compared to individuals receiving 2 or less cycles (adjusted odds ratio 0.40; 95% confidence interval 0.19-0.84). High adherence with TIS was also associated with lower outpatient service costs (IQR: $2,159-$8444 vs. $2,410-$14,423) and higher outpatient prescription drug costs (IQR: $35,125-$60,969 vs. $10,353-$46,768).

CONCLUSIONS: Use of TIS did not reflect recommended guidelines and may impact other health care utilization.