Table 2.

Parameter estimates for clearance maturation–decline function

Model parameter	Amoxicillin	Piperacillin	Meropenem	Pooled data
CLSTD (l h –1 70 kg –1 )	17.0 (8)	12.7 (9)	34.6 (193)	12.9 (6)
θ1	4.29 (34)	1.8 (31)	1.1 (26)	3.45 (77)
PMA50 (weeks)	49.0 (16)	71.6 (23)	398 (236)	49.7 (32)
θ2	1.95 (41)	13.8 (361)	1.11 (65)	4.0 (44)
AGE50 (years)	79.0 (14)	74.8 (27)	31.3 (257)	86.8 (9)
σ2	0.08	0.11	0.11	0.13

$$\mathit{CL}={\mathit{CL}}_{\mathit{STD}}.{\left(\frac{\mathit{WT}}{70}\right)}^{0.75}.\left(\frac{{\mathit{PMA}}^{{\theta }_1}}{{\mathit{PMA}}^{{\theta }_1}+{\mathit{PMA}}_{50}^{{\theta }_1}}\right).\left(1-\frac{{\mathit{AGE}}^{{\theta }_2}}{{\mathit{AGE}}^{{\theta }_2}+{\mathit{AGE}}_{50}^{{\theta }_2}}\right).exp\left(\epsilon \right)$$

Where: CL is the model predicted clearance; CL_STD is a standardized clearance; PMA is the postmenstrual age in weeks and PMA₅₀ is the PMA age at which 50% of adult function is achieved; AGE is the age in years and AGE₅₀ is the AGE at which 50% of decline has occurred; θs are Hill coefficients. σ² is the estimated variance of ε. Data presented above are mean parameter estimates (% relative standard error)