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BIOMD0000000321 - Grange2001 - L Dopa PK model

 

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Reference Publication
Publication ID: 11587490
Grange S, Holford NH, Guentert TW.
A pharmacokinetic model to predict the PK interaction of L-dopa and benserazide in rats.
Pharm. Res. 2001 Aug; 18(8): 1174-1184
PRNS Non-Clinical Drug Safety, F. Hoffmann-La Roche Ltd, Basel, Switzerland. susan.grange@roche.com  [more]
Model
Original Model: BIOMD0000000321.xml.origin
Submitter: Lukas Endler
Submission ID: MODEL1103250000
Submission Date: 25 Mar 2011 11:56:49 UTC
Last Modification Date: 06 Jun 2013 10:58:42 UTC
Creation Date: 27 Oct 2009 14:45:40 UTC
Encoders:  Lukas Endler
   Vijayalakshmi Chelliah
set #1
bqbiol:isVersionOf ICD G20
Gene Ontology dopamine uptake involved in synaptic transmission
bqbiol:occursIn Taxonomy Rattus norvegicus
Notes
Grange2001 - L-dopa PK model

A pharmacokinetics of L-dopa in rats after administration of L-dopa alone (this model: BIOMD0000000321) or L-dopa combined with a peripheral AADC (amino-acid-decarboxylase) inhibitor (BIOMD0000000320) has been studied using noncompartmental analysis.

This model is described in the article:

Grange S, Holford NH, Guentert TW
Pharmaceutical Research [2001, 18(8):1174-1184]

Abstract:

PURPOSE: To study the PK interaction of L-dopa/benserazide in rats. METHODS: Male rats received a single oral dose of 80 mg/kg L-dopa or 20 mg/kg benserazide or 80/20 mg/kg L-dopa/benserazide. Based on plasma concentrations the kinetics of L-dopa, 3-O-methyldopa (3-OMD), benserazide, and its metabolite Ro 04-5127 were characterized by noncompartmental analysis and a compartmental model where total L-dopa clearance was the sum of the clearances mediated by amino-acid-decarboxylase (AADC), catechol-O-methyltransferase and other enzymes. In the model Ro 04-5127 inhibited competitively the L-dopa clearance by AADC.

RESULTS: The coadministration of L-dopa/benserazide resulted in a major increase in systemic exposure to L-dopa and 3-OMD and a decrease in L-dopa clearance. The compartmental model allowed an adequate description of the observed L-dopa and 3-OMD concentrations in the absence and presence of benserazide. It had an advantage over noncompartmental analysis because it could describe the temporal change of inhibition and recovery of AADC.

CONCLUSIONS: Our study is the first investigation where the kinetics of benserazide and Ro 04-5127 have been described by a compartmental model. The L-dopa/benserazide model allowed a mechanism-based view of the L-dopa/benserazide interaction and supports the hypothesis that Ro 04-5127 is the primary active metabolite of benserazide.

The model has a species (A-dopa) whose initial concentration is calculated from a listOfInitialAssignments . While running for the first time the time-course (24hrs) for this model in COPASI (up to version 4.6, Build 33), the resulting graph displays only straight lines for all the species. Any subsequent runs should provide proper plots (i.e. without making any change to the model, just by clicking the "run" button again).

The above issue is caused by some initial assignments which are not calculated when COPASI imports the file. This issue should not be present in newer releases of COPASI.

To the extent possible under law, all copyright and related or neighbouring rights to this encoded model have been dedicated to the public domain worldwide. Please refer to CC0 Public Domain Dedication for more information.

Model
Publication ID: 11587490 Submission Date: 25 Mar 2011 11:56:49 UTC Last Modification Date: 06 Jun 2013 10:58:42 UTC Creation Date: 27 Oct 2009 14:45:40 UTC
Mathematical expressions
Reactions
L_Dopa absorption from gut hepatic and blood L-Dopa clearance L-Dopa clearance via AADC L-Dopa clearance via COMT
rest clearance of L-Dopa 3-OMD clearance    
Rules
Assignment Rule (variable: F_b) Assignment Rule (variable: F_H) Assignment Rule (variable: CL_H) Assignment Rule (variable: CL_dopa)
Assignment Rule (variable: f_rest) Assignment Rule (variable: CL_AADC) Assignment Rule (variable: CL_rest) Assignment Rule (variable: CL_COMT)
Physical entities
Compartments Species
gut A_dopa    
V_L_Dopa C_dopa    
V_3_OMD C_3-OMD    
Global parameters
F_b F_H F_G CL_H
Q f_H CL_dopa f_rest
f_AADC f_COMT CL_AADC CL_rest
CL_COMT CL_dopa0 ka_b CL_3_OMD
L_Dopa_per_kg_rat rat_body_mass    
Reactions (6)
 
 L_Dopa absorption from gut [A_dopa] → [C_dopa];  
 
 hepatic and blood L-Dopa clearance [A_dopa] → ;  
 
 L-Dopa clearance via AADC [C_dopa] → ;  
 
 L-Dopa clearance via COMT [C_dopa] → [C_3-OMD];  
 
 rest clearance of L-Dopa [C_dopa] → ;  
 
 3-OMD clearance [C_3-OMD] → ;  
 
Rules (8)
 
 Assignment Rule (name: F_b) F_b = F_H*F_G
 
 Assignment Rule (name: F_H) F_H = 1-CL_H/Q
 
 Assignment Rule (name: CL_H) CL_H = f_H*CL_dopa
 
 Assignment Rule (name: CL_dopa) CL_dopa = CL_AADC+CL_rest+CL_COMT
 
 Assignment Rule (name: f_rest) f_rest = 1-(f_AADC+f_COMT)
 
 Assignment Rule (name: CL_AADC) CL_AADC = CL_dopa0*f_AADC
 
 Assignment Rule (name: CL_rest) CL_rest = CL_dopa0*f_rest
 
 Assignment Rule (name: CL_COMT) CL_COMT = CL_dopa0*f_COMT
 
  Spatial dimensions: 3.0  Compartment size: 1.0
 
 A_dopa
Compartment: gut
 
 V_L_Dopa Spatial dimensions: 3.0  Compartment size: 0.496
 
 C_dopa
Compartment: V_L_Dopa
Initial concentration: 0.0
 
  Spatial dimensions: 3.0  Compartment size: 0.196
 
 C_3-OMD
Compartment: V_3_OMD
Initial concentration: 0.0
 
Global Parameters (18)
 
  F_b
Value: NaN   (Units: dimensionless)
 
  F_H
Value: NaN   (Units: dimensionless)
 
 F_G
Value: 0.24   (Units: dimensionless)
Constant
 
  CL_H
Value: NaN   (Units: l_per_h)
 
 Q
Value: 0.828
Constant
 
 f_H
Value: 0.13   (Units: dimensionless)
Constant
 
  CL_dopa
Value: NaN   (Units: l_per_h)
 
  f_rest
Value: NaN   (Units: dimensionless)
 
 f_AADC
Value: 0.69   (Units: dimensionless)
Constant
 
 f_COMT
Value: 0.1   (Units: dimensionless)
Constant
 
  CL_AADC
Value: NaN   (Units: l_per_h)
 
  CL_rest
Value: NaN   (Units: l_per_h)
 
  CL_COMT
Value: NaN   (Units: l_per_h)
 
 CL_dopa0
Value: 0.823   (Units: l_per_h)
Constant
 
 ka_b
Value: 2.11   (Units: per_h)
Constant
 
 CL_3_OMD
Value: 0.012
Constant
 
 L_Dopa_per_kg_rat
Value: 404.0
Constant
 
 rat_body_mass
Value: 0.25
Constant
 
Representative curation result(s)
Representative curation result(s) of BIOMD0000000321

Curator's comment: (updated: 28 Mar 2011 00:21:40 BST)

Time courses for a dose of 80 mg/kg L-Dopa as in figure 6 of the original article, has been reproduced here. The results were calculated using Copasi 4.6.33.

Due to problems with the use of initial assignments in Copasi, the model has to be evaluated once using either a short time-course simulation or a steady state computation to calculate and assign the correct starting values. After this, the model reproduces the correct results. Future versions of Copasi should not have this problem. The model was also tested with SBW 2.7.10, which did not exhibit this problem.

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