PHAR 4634 - Chapter 14 Page 7     ### Development of general equation

We can now consider a general equation which could describe the plasma concentration at any time after multiple IV. bolus drug administration.

Concentration at the end of the first dosing interval Equation XIV-11 Cp after the First Dose

where This gives the plasma concentrations at the end of first interval, where t is the dosing interval in hours.

At the start of the second interval  then at the end of the second dose interval and so on.

It will help if we define the parameter which is the fraction of the initial plasma concentration remaining at the end of the dosing interval.

Then  this is a geometric series with each term R times the preceding term.

Start Equation XIV-12 Cp Immediately after the nth Doses

End Equation XIV-13 Cp at the end of nth Dosing Interval

these two sums can be simplified to give

Start  Equation XIV-14 Cp at the Beginning on the nth Dosing Interval

and

End  Equation XIV-15 Cp at the End of the nth Dosing Interval

using the first equation (Equation XIV-14) we can calculate the concentration in plasma at any time following uniform multiple IV bolus administration. where t = time since the last dose. Then Equation XIV-16 Cp at any Time after n Doses

GENERAL EQUATION

This page was last modified: 12 February 2001

Copyright 2001 David W.A. Bourne     