Two compartment beaker model
Objective and introduction
Objectives
- To observe the time course of drug concentration in the centrl and peripheral compartments of a two-compartment system.
- To compare the time course after 3 types of input.
- Single Bolus Dose
- Single Bolus Dose and Constant Rate Infusion
- Single Bolus Dose plus First-Order and Constant Rate Infusion
Introduction
This is a practical session held in a laboratory. For health and safety reasons it is important to wear a lab coat and closed shoes.
Bring a printed copy of the lab instructions and read through them before you arrive at the lab.
Overview and assignment
Overview
- Start the experiment by adding doses of amaranth dye to the beaker system.
- Take samples from the central and tissue compartment beakers.
- Measure the absorbance of the samples using a spectrophotometer.
- Plot the time course of absorbance while the experiment is being performed,
- Construct a standard curve relating absorbance to amaranth dye concentrations on two occasions.
- Create a data set following the directions in the lab instructions.
- Use either MONOLIX and the beka_mlxt model (Figure 1) or NONMEM and the beka.ctl model (Figure 2) to estimate the parameters of the two compartment system.
- You will need to change the constants defining the 3 kinds of input in order to match the kinds of input you used for your experiment.
$PROBLEM BEKA two compartment model with bolus, zero-order and
first-order input
$MODEL
COMP=(AMTC) ; central
COMP=(AMTT) ; tissue
COMP=(AMTB) ; burette
$PSI
cl vc clic vt ; PK parameters
$PK
; Check these values match the experimental design
bolus=10 ; 10 mg bolus dose into central compartment
infrate=1 ; 1 mg/min infusion into burette
burdose=40 ; 40 mg bolus dose into burette
burvol=0.1 ; 0.1 L burette volume
burflow=0.01 ; 0.01 L/min burette flow
tk0=120 ; 120 min infusion from burette
$ODE
AMTC_0 = bolus
AMTT_0 = 0
AMTB_0 = infrate/burflow*burvol+burdose
CC=AMTC/vc
CT=AMTT/vt
CB=AMTB/burvol
;'t' is the name used by Monolix to
; refer to the data item defined as TIME.
if (t<tk0) then
ratein=burflow*CB
else
ratein=0
endif
DDT_AMTC = ratein + clic*CT - (cl+clic)*CC
DDT_AMTT = clic*(CC - CT)
DDT_AMTB = infrate - ratein
$OUTPUT
OUTPUT1 = AMTC/vc
OUTPUT2 = AMTT/vt
Figure 1. Code for beka_mlxt.txt
$INPUT ID TIME DVID ABS DV
$DATA beka.csv
$EST METHOD=COND INTER
MAX=9990 NSIG=3 SIGL=9 NOABORT PRINT=1
$THETA
(0,0.1,) ; CL
(0,1,) ; VC
(0,0.4,) ; CLIC
(0,4,) ; VT
$OMEGA 0 FIX ; PPV_CL
$SIGMA
1 ; RUVC_SD
1 ; RUVT_SD
$SUBR ADVAN13 TOL=9
$MODEL
COMP=(AMTC) ; central
COMP=(AMTT) ; tissue
COMP=(AMTB) ; burette
$PK
bolus=10 ; 10 mg bolus dose into central compartment
infrate=1 ; 1 mg/min infusion into burette
burdose=40 ; 40 mg bolus dose into burette
burvol=0.1 ; 0.1 L burette volume
burflow=0.01 ; 0.01 L/min burette flow
tk0=120 ; minutes of infusion from burette
cl=CL*EXP(PPV_CL)
A_0(1) = bolus
A_0(2) = 0
A_0(3) = infrate/burflow*burvol+burdose
$DES
CC=A(1)/vc
CT=A(2)/vt
CB=A(3)/burvol
; T is time used by differential equation solver
if (T<tk0) then
ratein=burflow*CB
else
ratein=0
endif
DADT(1) = ratein + clic*CT - (cl+clic)*CC
DADT(2) = clic*(CC - CT)
DADT(3) = infrate - ratein
$ERROR
CCONC = A(1)/vc
TCONC = A(2)/vt
if (dvid.eq.1) then
y=CCONC + RUVC_SD
else
y=TCONC + RUVT_SD
endif
$TABLE ID TIME Y dvid
NOPRINT ONEHEADER FILE=beka.fit
Figure 1. Code for beka.ctl
Assignment instructions are found in this document.