Study design and procedures
Information collected following review of the electronic medical record (EMR) included: baseline demographics, microbiologic data, lung function data, renal function data, and tobramycin dosing data. AUC24, Cmax, time undetectable, and all additional patient-specific pharmacokinetic parameters were calculated from two post-dose tobramycin serum concentrations using Excel©-based log-linear regression. Monitoring of tobramycin within this study typically adhered to our institution guidelines, which recommend obtaining levels four and ten hours following doses administered every 24 hours, and two and eight hours following doses administered every 12 hours. Per institution guidelines, patients typically had levels obtained after the third day of IV tobramycin therapy to allow for adequate rehydration. Doses were adjusted to achieve a target peak concentration of ≥12 mg/L (or eight to ten-fold the highest PsA MIC) and a trough concentration <0.5 mg/L. Institutional guidelines also recommend increasing the dosing frequency of IV tobramycin in patients who have a calculated time undetectable (concentration ≤0.5 mg/L) for longer than 8 hours within a 24-hour dosing interval.