Population Pharmacokinetic Analyses for Plazomicin Using Pooled Data from Phase 1, 2, and 3 Clinical Studies

Plazomicin is an aminoglycoside with activity against multidrug-resistant Enterobacteriaceae. Plazomicin is dosed on a milligram-per-kilogram-of-body-weight basis and administered by a 30-min intravenous infusion every 24 h, with dose adjustments being made for renal impairment and a body weight (BW) of ≥125% of ideal BW. A population pharmacokinetic analysis was performed to identify patient factors that account for variability in pharmacokinetics and to determine if dose adjustments are warranted based on covariates. The analysis included 143 healthy adults and 421 adults with complicated urinary tract infection (cUTI), acute pyelonephritis, bloodstream infection, or hospital-acquired bacterial pneumonia/ventilator-associated bacterial pneumonia (HABP/VABP) from seven studies (phases 1 to 3). A three-compartment structural pharmacokinetic model with a zero-order rate constant for the intravenous infusion and linear first-order elimination kinetics best described the plasma concentration-time profiles. The base structural model included creatinine clearance (CL(CR)) as a time-varying covariate for clearance. The covariates included age, BW, height, body surface area, body mass index, sex, race, and disease-related factors. The ranges of the α-, β-, and γ-phase half-lives for the analysis population were 0.328 to 1.58, 2.77 to 5.38, and 25.8 to 36.5 h, respectively. Total and renal clearances in a typical cUTI or HABP/VABP patient were 4.57 and 4.08 liters/h, respectively. Starting dose adjustments for CL(CR) are sufficient for minimizing the variation in plasma exposure across patient populations; adjustments based on other covariates are not warranted. The results support initial dosing on a milligram-per-kilogram basis with adjustments for CL(CR) and BW. Subsequent adjustments based on therapeutic drug management are recommended in certain subsets of patients, including the critically ill and renally impaired.