Mathematical description

The rate of change of the amount of the drug in the body can be expressed as:

dA

dt = -kA

Integration of the equation above yields:

InA = InA0-kt

which describes a linear relationship between InA and time.


A plot of InA versus time on a rectangular graph paper yields a straight line. The Y-intercept is equal to InA0 , and the slope is equal to -k.

Slope = -k
Ln A0

Since In A = 2.303 log A, the equation that describes the amount of the drug in the body at any, time can be expressed as:

log A = log A0 -

kt

2.303

which describes a linear relationship between log A and time.

A plot of log A versus time on a rectangular graph paper yields a straight line. The Y-intercept is equal to log A0 , and the slope is -k/2.303.

Slope = -k/2.303
Log A0