Tobramycin dosing
The mean daily dose of IV tobramycin was 12.3 mg/kg (standard deviation: 2.56) with the majority (84.8%) of patients receiving therapy every 24 hours. Within the pediatric cohort, the mean daily dose of IV tobramycin was 18.9% higher (13.8 mg/kg versus 11.6 mg/kg) than the adult cohort, and more frequently dosed multiple times daily (43.2% versus 3.7%) (Table 2 ). This difference is likely reflective of the augmented renal function and faster drug clearance in pediatric patients, resulting in a longer time undetectable and subsequent dose adjustment to increase dosing frequency per institutional guidelines. In those that developed AKI, the median total daily dose of 13 mg/kg did not vary greatly from 12 mg/kg in those who did not develop AKI.
AUC24 and Cmax
Of the patients encounters with an FEV1 that returned to baseline or improved following IV tobramycin therapy (n=91), 75.8% had an AUC24 ≥80 mg*hr/L (p=0.147) and 80.3% had a Cmax ≥8 times the highest PsA MIC (p=0.065) (Table 3 ). The mean Cmax in patient encounters where the FEV1 returned to baseline was 24.2 mg/L versus 21.6 mg/L in those in which the FEV1 did not return to baseline (p=0.186). The mean AUC24 in patient encounters with an FEV1 that returned to baseline was 122.3 mg/L versus 108.7 mg/L that did not return to baseline (p=0.141). Overall, there was a statistically significant correlation found between AUC24 and Cmax with an r2 value of 0.727 (p <0.001) (Figure 1 ).