PHARMACODYNAMICS ::
Pharmacodynamics is the branch of pharmacology which describes and explains the biochemical and physiological effects of drugs and their mechanism of action Thus this part includes : (1) Effects of drugs (2) Structure activity relationship (3) Drug-receptor interactions (4) Dose effect relationship and (5) Drugs interactions
A drug may produce its effect by combining with cell-enzymes cell-membranes or other specialized components of the cell The combination of drug with cell -component initiates a series of biochemical and physiological changes that are the characteristic of the drug The initial step i.e. interaction with cell or its component is termed as action of the drug and other events are effects of drugs for example acetylcholine combines with muscarinic receptors (this is the action ) and it decreases heart rate and fall in blood pressure (these are the effects )
The effects of drugs produced at the site of application are called local or topical effects The effects of drugs produced after its absorption are known as systemic effects
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