Pharmacokinetics of Telavancin in Adult Patients with Cystic Fibrosis during Acute Pulmonary Exacerbation

Adults with cystic fibrosis (CF) frequently harbor Staphylococcus aureus, which is increasingly antibiotic resistant. Telavancin is a once-daily rapidly bactericidal antibiotic active against methicillin-, linezolid-, and ceftaroline-resistant S. aureus. Because CF patients experience alterations in pharmacokinetics, the optimal dose of telavancin in this population is unknown. Adult CF patients (n = 18) admitted for exacerbations received 3 doses of telavancin 7.5 mg/kg of body weight (first 6 patients) or 10 mg/kg (final 12 patients) every 24 h (q24h). Population pharmacokinetic models with and without covariates were fitted using the nonparametric adaptive grid algorithm in Pmetrics. The final model was used to perform 5,000-patient Monte Carlo simulations for multiple telavancin doses. The best fit was a 2-compartment model describing the volume of distribution of the central compartment (V-c) as a multiple of total body weight (TBW) and the volume of distribution of the central compartment scaled to total body weight (V-theta) normalized by the median observed value (V-c = V-theta x TBW/52.1) and total body clearance (CL) as a linear function of creatinine clearance (CRCL) (CL = CLNR + CL theta + CRCL), where CLNR represents nonrenal clearance and CL theta represents the slope term on CRCL to estimate renal clearance. The mean population parameters were as follows: V-theta, 4.92 +/- 0.76 liters.kg(-1); CLNR, 0.59 +/- 0.30 liters.h(-1); CL theta, 5.97 x 10(-3) +/- 1.24 x 10(-3); V-p (volume of the peripheral compartment), 3.77 +/- 1.41 liters; Q (intercompartmental clearance), 4.08 +/- 2.17 liters.h(-1). The free area under the concentration-time curve (fAUC) values for 7.5 and 10 mg/kg were 30 +/- 4.6 and 52 +/- 12 mg.h/liter, respectively. Doses of 7.5 mg/kg and 10 mg/kg achieved 76.5% and 100% probability of target attainment (PTA) at a fAUC/MIC threshold of >215, respectively, for MIC of