Observation

Calculus is widely use in this process.
All these processes are depend upon differential equations which are important part of calculus.
These phenomenons are as below.....
When we take drugs, the concentration of the drugs in the blood is zero, as the drugs' chemicals move around the body and are metabolized, the concentration of the drug increases.
After sometime, The concentration no longer increases. From this point concentration begins to decrease.
There comes a point when the drug concentration no longer increases and begins to decreases. This is the period when the drug is fully distributed and metabolism is taking place.
As time goes, the drug concentration gets less and less and falls below a certain effective amount. So we need to to take more drug.
We can deal with such a situation with a differential equations.
It has two parts:

In first, Absorption takes precedence and after that elimination is the most important element.