T max calculation[1]

Determination of 풕_풎풂풙

1. Determination of   Prepared by: Imran Ahammad chowdhury

2. The rate of change of the amount of drug in the body after oral administration is a fraction of both the absorption rate and elimination rate That is- or, ………….. 1   Here, A=Amount of drug in the body  

3. Now How much drug is absorbed from the GIT, that means rate of absorption from the GIT is given by the following expression: ……. 2 So, from 1. 3   Similarly, rate of elimination  

4. From equation 2 in case of multiple oral dosage regimen, we can write, - - if fractio n of dose is absorbed.   Where, n=number of dose =dosing interval  

5. So, putting this value in equation 3 we get- = 4 Now, integration this equation we get, the general oral absorption equation for calculating the drug concentration ( ) in the plasma, at any time t, …. 5  

6. For a single oral dose, the equation can be written as follows- …. …… 6 The time needed to reach maximum concentration is independent of dose & is dependent on the rate constants for absorption ( ) & elimination (k). At the maximum concentration, the rate of drug absorbed is equal to the rate of drug eliminated. Therefore, the rate of concentration change is equal to zero.  

7. The rate of concentration change can be obtained by differentiating the equation 6. The rate of concentration change can be obtained by differentiating the equation 6. But at  

8. or, or , or , or , ( ) o r ,  

9. Thank you