Pharmacodynamics Overview

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Questions and Answers

What is the definition of pharmacodynamics?

Pharmacodynamics is the study of the biochemical and physiological effects of drugs on the body, and the mechanisms by which these effects are produced.

What are two main mechanisms of drug action?

Receptor mediated and non-receptor mediated (correct)

Hormonal and non-hormonal

Receptor-mediated and cellular-mediated

Physical and chemical

A receptor is a specific cellular structure, usually a protein, that binds a ligand. Ligands can include drugs, hormones and neurotransmitters.

True

Match the types of ligands with their definitions.

Agonist = A ligand that binds to a receptor and activates it, producing a biological response. Antagonist = A ligand that binds to a receptor but does not activate it. Instead, it blocks the action of an agonist. Partial agonist = A ligand that binds to a receptor and activates it, but produces a weaker response than a full agonist. Ligand = Any molecule that binds to a receptor. Signup and view all the answers

What are two factors that influence a ligand's ability to bind to a receptor?

Affinity and Efficacy Signup and view all the answers

An antagonist blocks an agonist's effect on the receptor.

True Signup and view all the answers

What are the two types of antagonists?

Competitive antagonists and Non-competitive antagonists Signup and view all the answers

What is a competitive antagonist?

A competitive antagonist binds to the same site on the receptor as the agonist but does not activate the receptor. It competes with the agonist for binding sites on the receptor. Signup and view all the answers

What is a pharmacological antagonist?

A pharmacological antagonist acts on the same receptor as the agonist, competing with the agonist for binding sites. Signup and view all the answers

What is a chemical antagonist?

A chemical antagonist interacts directly with the agonist, preventing it from reaching the receptor. Signup and view all the answers

What are some examples of drugs that act by physical means?

Demulcents (e.g., bismuth salts), adsorbents (e.g., charcoal), and lubricants (e.g., liquid paraffin) are examples of drugs that act by physical means. Signup and view all the answers

What is chelation?

Chelation is the ability of a drug to form a complex with a metal ion, effectively inactivating and excreting the metal from the body. Signup and view all the answers

Study Notes

Pharmacodynamics 1

Pharmacodynamics studies the drug's effect on the body
It's the relationship between drug concentration and the resulting biological effect.
The body and the drug interact in a cycle
Pharmacodynamics is distinct from pharmacokinetics, which describes how the body absorbs, distributes, metabolizes, and excretes a drug.

Drug Action

Mechanism of drug action is outlined
Including receptor-mediated and non-receptor-mediated mechanisms.
Types include Receptor-mediated, Non-receptor mediated, Pharmacological antagonists, Competitive antagonists
Non-competitive antagonists, Chemical antagonists, Physiological antagonists

Receptor-Mediated Mechanisms

Specific cellular structure (protein) binds to ligand (drug).
Ligand binding results in a response (action).
Ligands include agonists, partial agonists, and antagonists.

Ligands

Active part of drug
Binding to receptor results in response
Agonist—stimulates a response
Partial agonist—intermediate effect
Antagonist—blocks a response
Affinity measures binding ability
Efficacy measures response activation ability

Antagonism

Competitive antagonists compete with agonists for receptor sites.
Non-competitive antagonists bind to different sites, impeding agonist activity.

Types of Antagonism

Competitive antagonism—antagonist competes for receptor sites.
Non-competitive antagonism—antagonist binds to a different site, preventing action.
Chemical antagonism—antagonists neutralize a substance directly.
Physiological antagonism—antagonistic effects from separate mechanisms

Dose-Response Curves

Shows drug response versus dosage.
Important for understanding drug potency and efficacy.

Drugs Acting by Physical Means

Demulcents soothe tissue—Examples: bismuth salts coat the gastric mucosa.
Adsorbents absorb substances—Examples: charcoal adsorbs gases and toxins.
Lubricants allow easier movement—Examples: liquid paraffin lubricates.

Drugs Acting by Chemical Means

Antacids neutralize—Examples: neutralize stomach acid (HCl) in peptic ulcers.
Chemical Interactions—Examples: Protamine neutralizes heparin, an anticoagulant.

Chelation

Drugs to produce complex with metals to inactivate and excrete metal.
Used in treatment of metal poisoning.
Examples: Desferrioxamine treats iron poisoning, penicillamine treats copper poisoning (Wilson's disease).

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Description

This quiz explores the principles of pharmacodynamics, focusing on how drugs interact with the body and the mechanisms of drug action. It covers receptor-mediated mechanisms, the roles of ligands, and the difference between pharmacodynamics and pharmacokinetics. Test your knowledge on how drugs affect biological responses and the various types of antagonists involved.