Pharmacology 3- Agonism and Antagonism

Question 1

What is pharmacodynamics

Answer 1

How drugs effect the body

Involves qualitative and quantitive research to identify potential drug target.

Qualitative research to determine the mechanisms of action drugs.

Quantitative research to test drugs in humans to determine dosage, safety, contraindications, side effects and drug interactions

Question 2

What are the 4 types of drug targets.

Answer 2

Enzymes
Transporter proteins
Receptors
Ion channels

Question 3

Define ion channels

Answer 3

Ion channels - Activation through membrane voltage changesLocal anaesthetic agents can prevent opening of Na+ channels in nerves

Question 4

What are the 4 properties of drugs

Answer 4

1) Selectivity
2) Specificity
3) Potency
4) Efficacy

Question 5

Define drug selectivity

Answer 5

describes the ability of a drug to bind to a particular receptor. However some drugs bind to more than 1 receptor - thus have low selectivity.

Question 6

Define drug potency

Answer 6

Refers to dosage of drug needed to induce an effect.

Dependent on receptor affinity.A drug with low affinity will weakly bind to a receptor and will readily dissociate from that receptor – large dosages of that low affinity drug will be needed to induce an effect.A drug with high affinity will bind strongly to a receptor and stay bound to that receptor giving rise to a large physiological response at low concentrations.

Question 7

Define drug efficacy

Answer 7

Efficacy describes the ability of a drug to induce an effect.

Can have full agonist and partial agonist effect.

Question 8

What is full agonist

Answer 8

at specific doses can induce a full physiological response, i.e. a full and maximal muscle contraction.

Question 9

Define partial agomsit

Answer 9

describes a drug that cannot induce a full physiological response regardless of the dose.

Question 10

Why is partial agonist useful in healthcare

Answer 10

because they can have a therapeutic effect without a risk of overdose.

Question 11

Define agonists

Answer 11

These are stimulant molecules – they elicit biological responses in intact cells/tissues.

Question 12

Define antagonism

Answer 12

Situation where effect of one hormone, neurotransmitter or drug (agonist) is reduced or abolished by presence of a second drug (antagonist).

Question 13

What are the 5 mechanisms for drug antagonism

Answer 13

1) Chemical antagonism - when drugs reduce the concentration of an agonist.
2) Receptor antagonism – Competitive antagonism
3) Non- competitive antagonism
4) Pharmacokinetic antagonism
5) Physiological antagonism

Question 14

Define a competitive receptor antagonism

Answer 14

Describes the blockade of a receptor by a drug molecule.Antagonists have no efficacy, but have affinity.Antagonist competes with the agonist for receptor site – thus called competitive antagonism. Affinity can vary. Relatively low affinity – Reversible competitive antagonism.High affinity – Irreversible competitive antagonism.

Question 15

Define non competitive anatagomsim

Answer 15

Drug binds to an allosteric site (non-agonist) site on the receptor and prevents activationConverts a full agonist into a partial agonist.

Question 16

Define the difference between pharamcokinetics and physiological antagonism

Answer 16

Pharmacokinetic Antagonist drug acts to increase clearance, reduce plasma concentrations and affect half life of active drug in the body.Physiological AntagonismInteraction between two drugs that initiate opposing effects via different receptors in the same target tissue.