Application of PK to Patient Dosing

Question 1

Why do we design a dosing regimen?

Answer 1

To maintain Css,avg at desired levels and stay within the therapeutic range

Question 2

First step

Answer 2

Choose the desired Css, avg by finding the geometric mean of the peak and trough drug concentrations

Question 3

Second step

Answer 3

Calculate tau using Css,min and Css, max and Tau max formula

Question 4

What is the tau max formula?

Answer 4

Tau max = 1.44 * t1/2 * lnCss,max/Css,min

Question 5

What are three rules related to Tau?

Answer 5

• it can be no longer than Tau max
• Tau can be only 24, 12, 8, or 6 hours
• biggest Tau is required

Question 6

Third step

Answer 6

Determine dosing rate needed to achieve target Css,ave
dosing rate=D/tau=Cl* Css,avg / SF

Question 7

Fourth step

Answer 7

Multiply Tau * the dosing rate to determine your dose
- choose dose based on available dosage forms

Question 8

Fifth step

Answer 8

Double-check calculations. Make sure that Css,min and Css,max are within the therapeutic range. Apply the Css,min, Css,max, Css,avg formula.