TABLE III.

Population pharmacokinetic parameters for mitoxantrone and etoposide in presence and absence of valspodar

MITOXANTRONE
Parameter	Estimate	% CVa	Interindividual variability estimateb	%CVc
CL0 (L/h)	16.4	17.9	48.1	69
CL1 (L/h)	5.88	30.8
V1 (L)	23.2	19.3	64.4	68.5
V2 (L)	102	19.9	-	-
Q (L/h)	8.13	23.7	-	-
EC50mitox (mg/L)	0.525	121	-	-
Residual errord	60.6%	17.8	-	-

ETOPOSIDE
PK parameter	Estimate	% CVa	Interindividual variability estimateb	%CVc
CL0 (L/h)	1.52	0.36	61.56	5.83
CL1 (L/h)	0.611	0.37
V1 (L)	3.58	0.18	98.5	4.56
V2 (L)	3.82	0.35	-	-
Q (L/h)	2.38	0.428	-	-
EC50eto (mg/L)	0.271	0.53	-	-
Residual errord	32.1%	0.43	-	-

V1 = volume of the central compartment, V2 = volume in the peripheral compartment, Q = inter-compartmental clearance, CL = clearance from the central compartment, CL₀ is the baseline clearance and CL₁ is the asymptotic value of CL for large concentrations of valspodar (when valspodar →∞), EC_50mitox= the concentration of valspodar required to reduce mitoxantrone clearance by 50%, EC_50eto= the concentration of valspodar required to reduce etoposide clearance by 50%.

^aRelative standard error of estimate (SE estimate/estimate) expressed as a percentage

^bEstimates of variability, expressed as % (100×√variance)

^cPercent square root of the relative standard error of the coefficient of variation($100\sqrt{{}^{\mathit{SE}\text{estimate}}∕_{\text{estimate}}}$)

^dResidual intrasubject variability