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

Description

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,

		k=ln(2)/thalf;

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 
dose). 

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. 

Equations

None.

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.