pharmacodynamics

pharmacodynamics

• what drug does to the body

types of pharmacological action of drugs

• via direct effects on cellular receptor function

• via action on ion channels

• via action on membrane transport processes

• via enzyme inhibition

drug action: targeting cellular receptors

• receptors are specific proteins with distinct binding sites and signal transduction properties

• situated in cell membranes (fast responses)

• situated in cytoplasm (slow responses)

• ligands or binding partners for receptors include:

  • agonists

  • antagonists

  • partial agonists

receptor agonist

• molecules that binds to a receptor and activates it

partial agonist

• agonist that can’t elicit the same level of biological response as a full agonist

agonist effect

• diminish or abolish effect of an agonist via interaction with its receptor

competitive antagonists

compete for the same binding sites as that for the agonist

non competitive antagonists

alter the receptor binding site fit for the agonist, reducing agonist activity

targeting ion channels

• ion channels influence the movement in and out of cells across cell membranes

• ion movement influences polarisation of excitable cell membranes and intracellular signalling cascades

• drugs acting on ion channels can affect neural transmission and smooth muscle contractibility

drug action targeting transporter function

• transporters mediate the movement of specific endogenous signalling molecules and nutrients in and out of cells

• Eg SSRIA drug fluoxetine blocks the neuronal SERT leading to retention in neural synaptic cleft