Mechanisms of drug action

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Mechanisms of drug action:

1- Interaction with cell surface receptors:

  Cell surface receptors may be proteins or glycoproteins. Drug binding to these

receptors is highly specific and depends on the chemical structure of the drug. Drug

binding to the receptor is attained by several types of interactions including

hydrophobic interactions, van der Waals forces, hydrogen bonds, ionic bonds and

covalent bonds. 

  Cell surface receptors are composed of extracellular domains that bind the drug

or the endogenous molecule. The ligand binding may act as a triggering signal  that

can be propagated in the target cell through intracellular regulatory molecules known

as  second messengers  or  effectors.  For example, isoproterenol binds with β

adrenergic receptors which are functionally coupled  to adenylate cyclase via the

stimulatory G protein (GS).  As a result, adenylate cyclase  is activated and cyclic

adenosine monophosphate (cAMP) level increases. 

2- Interaction with enzymes:

  Enzyme activation by drugs may be caused by allosteric binding in which a

drug is bound to an allosteric site of the enzyme resulting in conformational changes

of the enzyme and increased affinity of the endogenous substrate to the active site of

the enzyme.  

 

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