TABLE 2

Final population PK model parameter estimates and standard errorsa

ParameterPopulation mean (%CV)Magnitude of IIV (%CV)
Final estimateBootstrap %SEMFinal estimateBootstrap %SEM
CLR (liters/h) coefficient3.633.150.0122 (11.0)33.3
PEDS shift−0.33522.9
CLCR power0.33751.3
IOV1.00.0115 (11.0)20.2
Vc (liters) coefficient4.724.840.0351 (18.7)30.4
CLd (liters/h) coefficient7.8911.0
Vp (liters) coefficient3.703.52
Residual-variability model
Constant CV component0.0112 (10.6)10.5
Additive component0.84548.5
  • a Cefazolin total clearance is calculated as CL = [0.153 + 3.63 × (CLCR/90)0.75(1 − 0.335 × PEDS) × exp(IIV + IOV × day), where CLCR is creatinine clearance in ml/min/1.73 m2, PEDS (population indicator variable) = 0 for an adult subject, PEDS = 1 for a pediatric patient, day = 0 for day 1, and day = 1 for day 11. The cefazolin V1 and apparent volume of distribution in the peripheral compartment are multiplied by (WTKG/70)1, where WTKG is weight in kg. The cefazolin CLd (distribution clearance) coefficient is multiplied by (WTKG/70)0.75. Residual variability, calculated as [(Cpij × σCCV + σadd)/Cpij] × 100 (where σCCV is the constant CV component and σadd is the additive component), was 95.1, 19.1, 11.4, and 10.8% CV for plasma cefazolin concentrations (Cpij) of 1, 10, 100, and 500 mg/liter, respectively.