Therapeutic drug concentration

Therapeutic drug concentrations

The goal of drug treatment is to achieve a drug concentration within the body that is therapeutically relevant and appropriate. A relationship exists between the concentration of the drug in the body and the pharmacological effect. As can be seen in the graphic, a drug that achieves concentrations represented by the orange line is pharmacologically favourable over those represented by either the white or the yellow line.

Using morphine as an example, the goal is

to achieve concentrations in the therapeutic index and avoid 1) overdosing (yellow line), which would cause respiratory depression and 2) underdosing (white line), which would leave the patient without symptomatic relief. So how do we determine the appropriate dose and maintain drug concentrations in the therapeutic index despite processes constantly eliminating the drug from the body? These answers are addressed as the basic concepts of pharmacokinetics are explored.