PURPOSE: Cystic fibrosis (CF) patients receiving tobramycin for an exacerbation are dosed by pharmacists using a nomogram and doses are adjusted based on levels. The primary objective is to evaluate the efficacy of the CF dosing nomogram in attaining therapeutic peaks based on the initial regimen. Secondary outcomes include the prevalence of attaining target troughs, attaining combined peak and trough targets, the incidence of nephrotoxicity, and identifying factors impacting levels. METHODS: A

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... retrospective medical record review was conducted for adult patients with CF who received tobramycin from . Inclusion criteria were an intravenous tobramycin dose of at least 10 mg/kg and at least two serum tobramycin concentrations. Patients were excluded if dosing deviated from the nomogram. Descriptive statistics and the chi-square test were used for analysis. RESULTS: Of the 322 patients screened, 190 met the inclusion criteria with a mean age of 26 years, 52% male, mean body mass index of 19.7, and mean baseline creatinine clearance of 110 mL/ minute. With their initial dosing regimen, 41% of patients had a therapeutic tobramycin peak, 61% had a therapeutic tobramycin trough, and 22% had both a therapeutic peak and trough. About 10% of patients experienced nephrotoxicity within 7 days and 5.5% had AKI within forty-eight hours. Factors contributing to a supratherapeutic trough include female gender (p = 0.01), body mass index (BMI) (p < 0.0001), and baseline creatinine clearance (p = 0.0013). BMI is the only factor that increased the chance of attaining a therapeutic peak (p = 0.045). CONCLUSION: Results indicate that the current dosing nomogram does not routinely achieve target peak concentrations with the initial regimen.