Pharmacodynamics

study of the biochemical and physiologic effects of drugs and the molecular mechanisms by which those effects are produced.

relationship between the size of an administered dose and the intensity of the response produced

patients response gets more intense with increased dosage

largest effect a drug can produce

• the amount of drug given to elicit an effect
• a potent drug gives its effects in low doses
• Drug A can be more effective than drug B even though drug B may be more potent.

hormones, neurotransmitters, and other regulatory molecules.

• 1,Cell membrane–embedded enzyme.
• 2, Ligand-gated ion channel.
• 3, G protein–coupled receptor system (G = G protein).
• 4, Transcription factor.

highly desirable characteristic of a drug, in that the more selective a drug is, the fewer side effects it will produce

• when a drug interacts with a receptor type that regulates multiple processes
• when a drug interacts with multiple receptors

• Strength of attraction between its drug and receptor
• *drugs with high affinity are very potent
• *drugs with high affinity are effective in low doses

• ability of a drug to activate its receptor upon binding
• *Drugs with high intrinsic activity have high maximal efficacy

• Drugs that mimic the body's own regulatory molecules
• agonists activate the receptor
• have high affinity
• have high intrinsic activity

• Drugs that block the actions of endogenous regulators are called antagonists.
• Lack of intrinsic activity results in lack of receptor activity

how much agonist is present

• produce a receptor blockade by competing with agonists.
• the receptor is occupied by whichever agent is in higher concentration.

• an agonist with moderate intrinsic activity.
• Maximal effect is lower than a full agonist
• can act as agonists (if no full agonist is present) & antagonists (if a full agonist is present)

(Refractoriness) results from continuous exposure of cell receptors to an agonist

Results from continuous exposure of cell receptors to antagonist

(ED 50) dose required to produce a defined therapeutic response in 50% on the population.

ED50:LD50 ratio between average effective dose & average lethal dose

• Wide= safe
• Narrow= unsafe