Population Pharmacokinetics of Enteric-Coated Mycophenolate Sodium in Children after Renal Transplantation and Initial Dosage Recommendation Based on Body Surface Area

Table 2

Parameter estimates from the base model and final model.

Parameters	Base model		Final model
	Estimate	RSE/%	Estimate	RSE/%
Structure model parameters
𝜃ka1	0.112	21.4	0.123	20.5
𝜃Tk02	1.03	69.7	2.90	42.1
𝜃F	0.644	6.12	0.553	6.30
𝜃Tlag1	8.40	7.71	8.45	9.30
𝜃diffTlag2	5.76	16.5	5.78	18.0
𝜃V	4.63	22.6	3.73	13.0
𝜃CL	4.29	7.43	4.28	6.53
𝜃CL-BSA	\	\	1.30	20.4
Interindividual variability
𝜔ka1	1.14	15.7	0.885	15.2
𝜔Tk02	3.34	40.5	2.31	19.1
𝜔F1	0.747	18.4	0.513	18.8
𝜔Tlag1	0.478	11.4	0.576	11.3
𝜔diffTlag2	0.688	24.7	0.941	33.6
𝜔V	0.840	18.3	0.337	26.3
𝜔CL	0.504	10.1	0.481	13.3
Residual error model parameters
	0.0709	41.4	0.0631	25.2
	0.199	7.57	0.199	7.5

This PK model has a double extravascular absorption composed of a first-order absorption (rate constant , fraction ) with a lag time () and a simultaneous zero-order absorption (duration , fraction 1-) with a lag time longer than the first delay (). The PK model has a central compartment (volume ) and a linear elimination (clearance CL). The final model included body surface area (BSA) as the covariate for CL. Final model equations: , , , , , , . 𝜃_ka1, 𝜃_Tk0, 𝜃_F, 𝜃_Tlag1, 𝜃_diffTlag2, 𝜃_V, and 𝜃_CL are typical values of , , , , diffTlag2, , and CL, respectively; 𝜃_CL-BSA is the typical value of the power of the covariate BSA for the CL. 𝜔_ka1, 𝜔_Tk02, 𝜔_F1, 𝜔_Tlag1, 𝜔_diffTlag2, 𝜔_V, and 𝜔_CL are standard deviations of interindividual random effects of the ka1, Tk02, , Tlag1, diffTlag2, , and CL, respectively. and are residual error model parameters from the equation ; sqrt: square root; 𝜀 is a normally distributed variable that has a mean of 0 and a standard deviation of 1. RSE: relative standard error.