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 in the blood plasma - and the pharmacological effect. As can be seen in the graphic, a drug that achieves concentrations represented by the green line is pharmacologically favourable over those represented by either the red or blue line.
Using morphine as an example, the goal is to achieve concentrations in the therapeutic index and avoid 1) overdosing (red line), which would cause respiratory depression and 2) underdosing (blue 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.