AUC Calculation using Trapezoidal Rule

IV Bolus - Linear One Compartment

A dose of 150 mg was administered to healthy volunteer. Seven blood samples were collected at 0.5, 1, 2, 4, 6, 8, 10 hours. Plasma was separated from each blood sample and analyzed for drug concentration. The collected data are shown in the table below.

Time (hr) Cp (mg/L) Δ (AUC mg.hr/L) AUC (mg.hr/L)
 
0
 
     
 
0.5
 
8.41    
 
1
 
8.47    
 
2
 
7.04    
 
4
 
5.4    
 
6
 
3.56    
 
8
 
2.44    
 
10
 
2.21    
 

 
     

The table above provides a set of data for you to analyze. Use these data with the trapezoidal rule shown in the equations below to calculate each AUC segment including the last segment. The first segment is calculated using the concentration at time zero calculated by (back) extrapolation from the data provided. The data should be plotted on semi-log graph paper and a best-fit line drawn through the data. The point where this line crosses the y-axis is the y intercept or your estimate of Cp(0). Use a point on the other end of the line and calculate kel with the equation below. Estimate the area from zero to the last data point using the trapezoidal rule. Add the area for the last segment to get the total area under the curve.


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Some Useful Equations

Delta AUC trapezoidal rule equation

Don't forget the first and last segments. You will need to extrapolate the concentration back to the intercept for the first segment. You will also need kel to calculate the last segment:

Equation for the last AUC segment

Calculate kel from points on the best-fit line.

kel from semi-log plot


Last update: Wed 26 Jun 2013 12:14:41 pm
Copyright © 2002-14 David Bourne (david@boomer.org)