Module 5. Species differences in pharmacokinetics (Cats are not small dogs).

Objectives

Having completed this exercise and based on pharmacokinetic constants and data, students should be able to:

Significance

Pharmacokinetic parameters and dosage recommendations are taken from the USP Veterinary Drug Monograph "Chloramphenicol" (http://www.aavpt.org/associations/12658/files/chloramphenicol.pdf)

Exercise

Download chloramphenicol.xlsx, (the worksheet for this module). Depending on the security setting of your computer, you may have to "enable editing" in order to make the changes suggested by the exercise.

Pharmacokinetic variables for the "Dog" simulation values published for dogs. Pharmacokinetic variables for the "Cat" simulation are values published for cats.

Doses and intervals for both simulations are set to 50 mg/kg q8H (typical dog dosing regimen).

Target concentrations

Manipulate the dosage

Step 1: Before you make changes, review pharmacokinetic variables, calculated values and steady state calculated values.

Step 2: Enter the "recommended" cat dose for simulation #2.

Step 3: Enter the "high" cat dose for simulation #2.

Inspect

Calculated values

Step 1, 2 & 3:

Steady-State Concentrations (for repeated doses during therapy).

Step 1:

Step 2:

Step 3:

Graphs

Step 1:

Step 2:

Step 3:

Assess

Questions (Key)

  1. Based on the information presented in this module does it appear that chloramphenicol can be given to cats in a way that is as effective, as safe and as practical as it is given to dogs?
  2. This quote appears in cat "usual dose" section(s) of the USP monograph for Chloramphenicol: "Doses of 25 to 50 mg per kg of body weight every twelve hours have been recommended, and may be necessary for some infections, but could increase the risk of side effects". In terms of the plasma concentration vs time profile, why might 50 mg/kg be a more effective dose?
  3. Based on the same USP quote in question 2 and in terms of the plasma concentration vs time profile, why might 50 mg/kg be a more toxic dose?