Model number


The half-life for ingestion of low, middle, and high concentrations of Salicylic acid are computed for three separate experiments.


Assume the removal of salicylic acid from the plasma in a human
body is a simple decay process. The governing equation would be

		d[SA]/dt = -k*[SA].

where k is the rate constant and [SA] is the concentration of
salicylic acid.

Given the initial condition at t=t.min (time=0)
SA=SA0, the solution is

		[SA(t)] = SA0*exp(-k*t).

The equation for the half life is

		SA0/2 = SA0*exp(-k*thalf). Solving for k,


The data for  low dose aspirin ingestion [Benedek et al., 1995] is 
based on averaged plasma concentrations from 10 healthy male 
volunteers who ingested an 80 mg tablet of aspirin. The last  seven 
points were digitized from the authors' figure (their Figure 1, 
right panel, dose period 1, open squares). 

The data for mid dose aspirin ingestion [Aarons et al., 1989] is 
based on averaged plasma concentrations from 9 female and 9 male 
healthy volunteers, who ingested 1000 mg of lysine acetyl salicylate. 
The last eleven points were digitized from authors' figure (their 
Figure 4, the solid triangles indicating oral administration of the 

The data for  the high dose aspirin ingestion [Prescott et al., 1982] 
is based on averaged plasma concentrations from 16 patients being 
treated for mild salicylism (plasma salicylate concentrations 
250-400 mg/L). The last nine points were digitized from authors' 
figure (their Figure 1, open circles). In the aspirin overdose cases,
the authors were attempting to discern best treatment methods. 

fig 1



The equations for this model may be viewed by running the JSim model applet and clicking on the Source tab at the bottom left of JSim's Run Time graphical user interface. The equations are written in JSim's Mathematical Modeling Language (MML). See the Introduction to MML and the MML Reference Manual. Additional documentation for MML can be found by using the search option at the Physiome home page.

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1. Aarons L, Hopkins K, Rowland M, Brossel S, Thiercelin JF.  Route 
of administration and sex differences in the pharmacokinetics of 
aspirin, administered as its lysine salt. Pharmaceutical Res 6: 
660-666, 1989

2. Benedek IH, Joshi AS, Pieniaszek HJ, SY King SY,  Kornhauser DM. 
Variability in the pharmacokinetics and pharmacodynamics of low dose 
aspirin in healthy male volunteers. J.  Clin. Pharmacol 35: 1181-1186, 

3. Prescott LF, Balali-Mood M, Critchley JA, Johnstone AF, Proudfoot AT. 
Diuresis or urinary alkalinisation for salicylate poisoning? Br Med J 
(Clin Res Ed). 1982 November 13; 285(6352): 1383–1386.
Key terms
salicylic acid
half life

Please cite in any publication for which this software is used and send one reprint to the address given below:
The National Simulation Resource, Director J. B. Bassingthwaighte, Department of Bioengineering, University of Washington, Seattle WA 98195-5061.

Model development and archiving support at provided by the following grants: NIH U01HL122199 Analyzing the Cardiac Power Grid, 09/15/2015 - 05/31/2020, NIH/NIBIB BE08407 Software Integration, JSim and SBW 6/1/09-5/31/13; NIH/NHLBI T15 HL88516-01 Modeling for Heart, Lung and Blood: From Cell to Organ, 4/1/07-3/31/11; NSF BES-0506477 Adaptive Multi-Scale Model Simulation, 8/15/05-7/31/08; NIH/NHLBI R01 HL073598 Core 3: 3D Imaging and Computer Modeling of the Respiratory Tract, 9/1/04-8/31/09; as well as prior support from NIH/NCRR P41 RR01243 Simulation Resource in Circulatory Mass Transport and Exchange, 12/1/1980-11/30/01 and NIH/NIBIB R01 EB001973 JSim: A Simulation Analysis Platform, 3/1/02-2/28/07.