Pharmacodynamics

Pharmacodynamics (Greek: dynamis-power) : It refers to What the drug does to the body.
This includes physiological and biochemical effects of drugs and their mechanism of action at macromolecular/ subcellular/ organ system levels, eg. Adrenaline interacts with adrenoceptors resulting in G-protein mediated stimulation of cell membrane bound adenylyl cyclase which further results in increased intracellular cyclic 3',5' AMP that results in cardiac stimulation, hepatic glycogenolysis and hyperglycemia, etc.