Download - Medication Model
7/21/2019 Medication Model
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System Dynamics (VenSim) Challenge: Apprenticeship Level 1
Simulating Therapeutic Medication Levels
Background Reading
Dr. Brocket practices internal medicine in a maor So!th "astern city. #ne day $s.
%omes came in &or a check!p and descri'ed the symptoms o& a serio!s kidney condition.
he medication that is !sed to treat her kidney condition isnt e&&ective !ntil the patienthas at least 1** milligrams in her 'ody. +& the medicine level reaches a'ove ,**
milligrams- it 'ecomes toic to the 'ody. he 'ody meta'oli/es ('reaks do0n) and
ecretes this medication at a rate o& 1* o& the amo!nt in the 'ody every ho!r. Dr.
Brocket needs to prescri'e the medication in the proper dosage so $s. %omes 0ill get0ell and not have harm&!l side e&&ects &rom an overdose.
Certification Challenge
2o!r task is to constr!ct a VenSim model that 0ill prod!ce the graph 'elo0 and help Dr.
Brocket &ind a dosage rate that is sa&e- e&&ective and convenient &or $s. %omes to takedaily.
3e are interested in the val!es held in the &ollo0ing reservoir: 1.$edication level
At the 'eginning o& the model- the medicine level reservoir contains these val!es:
1. $edication Level: *
4or the medication reservoirs- here is a description o& the in&lo0s and o!t&lo0s:1. $edication Level: he medication reservoir has 5 rates- one coming in and one
going o!t.
A. ake pills: an in&lo0 (a 6rate7 in VenSim notation). he take pills
in&lo0 depends on 8 a!iliary varia'les:
i. Start taking: this is the time it takes $s. %omes to get her prescription &illed and take her &irst dose. Set the initial val!e to
,.
ii. ime 'et0een dosages: this is the n!m'er o& ho!rs $s. %omes0aits 'et0een dosages. Set the initial val!e at 5, or once a day.
iii. Dosage: this is the n!m'er o& mg o& medicine that $s. %omes
takes 0ith each dose. Set the initial val!e at 5**.he &orm!la in take pills is 9 ;LS" <A+=( >start?start taking -
>d!ration?*.5@- >repeattime?time 'et0een dosages - >end?1** )dosage.
he d!ration is set to *.5@ the time step. he end is set to 1** ho!rs the
end o& the sim!lation.
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B.
"creted: an o!t &lo0. "creted depends on the a!iliary varia'le
ecretion rate. he ecretion rate is set at .1 or 1*. he &orm!la inecreted is9 $edication levelecretion rate.
here are 5 other important &actors:
1. herape!tic level: an a!iliary varia'le set at 1**.
5. oic level: an a!iliary varia'le set at ,**.
he time !nit &or this model is ho!rs- and 0e 0ant to r!n it &rom * to 1** ho!rs or !st
over , days. 2o!r time step sho!ld 'e set to .5@. 2o!r model sho!ld have:
1 'o varia'le
5 rates a!iliary varia'les
@ connectors
3hen yo! r!n yo!r model- it sho!ld prod!ce a graph that looks like the one 'elo0:
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