Pharmacokinetics and pharmacodynamics for VNs: 2

This second article describing key pharmacological principles focuses on pharmacodynamics, the physiological effects of drugs on the body. It follows on from the first article, which discussed important pharmacokinetic principles, particularly in relation to anaesthetic and analgesic drugs. It is important to have knowledge of both pharmacokinetics and pharmacodynamics in order to fully understand the effects of individual drugs on the body.

Generally, in order for a drug to exert an effect on the body, the drug must bind to a receptor. The word ‘receptor’ can be used to describe all target molecules for drug binding, and it is used in this context in this article. Receptors as a group can, however, be divided up into: true receptors, which are usually protein molecules on cell membranes; enzymes, which can be located intra or extracellulary; ion channels in cell membranes; and transport proteins, which are located in cell membranes.

Once the drug has bound to the receptor there is a transduction pathway that precedes drug effect, the time lag between drug binding and drug effect depends on the nature of the transduction pathway.