Module 1. Effect(s) of dose manipulation on plasma concentrations.

Objectives

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

Significance

A veterinarian needs to appreciate the results of dose manipulation (in terms of plasma concentrations). Under normal circumstances doubling the dose doubles the plasma concentrations at all time points on the concentration versus time profile. This means that the pharmacokinetic constants did not change with a change in dose This is what is meant by "dose independent" pharmacokinetics. Certain misconceptions arise concerning the effect of increased dose on the duration of effect. It may seem logical to assume that doubling the dose of a drug will double its duration. In fact, doubling the dose of a drug usually extends its duration by one drug half-life.

Exercise

Download dose.xlsx, the worksheet for this module. Depending on your settings, you may have to "enable editing" in order to make the changes suggested by the exercise.

Pharmacokinetic variables on the worksheet are preset for a typical adult dog given an aspirin. Please note, the dose and interval were chosen for the purposes of this exercise and are not the only appropriate dose regimen for dogs.

Target concentrations

Manipulate the dosage

Inspect

Calculated values

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

Graphs

Assess