Pharmacodynamics is what the DRUG does to the BODY. It explains the relationship between drug concentration and the effect produced at the receptor or tissue level.
Pharmacology Basics
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Pharmacodynamics is what the DRUG does to the BODY. It explains the relationship between drug concentration and the effect produced at the receptor or tissue level.
Agonist
Binds a receptor and ACTIVATES it to produce a response.
e.g., Albuterol activates Ξ²2 receptors β bronchodilation
Antagonist
Binds a receptor and BLOCKS it, preventing activation.
e.g., Naloxone blocks opioid receptors β reverses overdose
Affinity
How tightly a drug binds to its receptor.
Efficacy
The maximum effect a drug can produce.
Potency
The amount of drug needed to produce a given effect (lower dose = more potent).
e.g., Fentanyl is more potent than morphine β smaller dose, same effect
Therapeutic Index (TI)
Ratio of toxic dose to effective dose. A LOW TI = narrow safety margin.
Tolerance
Decreased response over time β higher dose needed (e.g., opioids, nitrates).
Dependence
Physical/psychological need for the drug; withdrawal occurs if stopped.
These drugs have a small margin between effective and toxic dose β monitor levels:
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