Dose-Response Curves

To define and explain dose-effect relationships of drugs, including dose-response curves with reference to: graded and quantal response.

Standard Dose-Response Curves

A dose-response curve is a graph of concentration against the fraction of receptors occupied by a drug.

Log-Dose Response Curves

It is difficult to compare drugs using standard dose-response curves. Therefore, dose is commonly log-transformed to produce a log-dose response curve.

This curve:

• Compares log-dose versus clinical effect
• Demonstrates that the blue drug has greater potency than the red drug, though both are full agonists

Responses can be either graded or quantal:

• Graded responses demonstrate a continuous increase in effect with dose
  • E.g. Blood pressure and noradrenaline dose
• Quantal responses demonstrate a response once a certain proportion of receptors are occupied
  Examples include:
  • ED₉₅
    Median dose of neuromuscular blocker required to produce a 95% loss of twitch height.
  • MAC
    Mean alveolar concentration of agent required to prevent movement in response to a surgical stimulus.

References

1. Anderson C. Pharmacodynamics 1. ICU Primary Prep. Available at: https://icuprimaryprep.files.wordpress.com/2012/05/pharmacodynamics-1.pdf