Drug-receptor interactions

Question 1

Give a definition for a ‘drug’

Answer 1

Chemical substance that interacts with a biological system to produce a physiological effect

Question 2

Define 1. Pharmacodynamics and 2. Pharmacokinetics

Answer 2

1. the effect of the drug on the body

2. the effect that the body has on the drug

Question 3

State the four types of drug target sites

Answer 3

Receptors
Ion channels
Transport systems
Enzymes

Question 4

State the four types of receptors

Answer 4

G-protein coupled
Receptor-operated channel
DNA-coupled receptor
Receptors that are enzymes (e.g. tyrosine kinase)

Question 5

What are the two types of ion-channels?

Answer 5

Voltage sensitive

Receptor-linked

Question 6

What are the three ways in which drugs can interact with enzymes?

Answer 6

Enzyme inhibitors
False substrates
Prodrugs (first converted to active form in body)

Question 7

What is a common example of the unwanted effects of drug interaction with enzymes?

Answer 7

Paracetamol overdose => saturation of microsomal enzymes in liver so the paracetamol is then broken down by another set of enzymes (P450) which generate toxic metabolites

Question 8

Give two examples of drugs with ‘non-specific’ drug action due to their physiochemical properties

Answer 8

Antacids

Osmotic purgatives

Question 9

Define agonist

Answer 9

A ligand that binds to and activates a receptor to generate a cellular response

Question 10

Define antagonist

Answer 10

A ligand that binds to a receptor to prevent generation of a cellular response (affinity but no efficacy)

Question 11

What does the potency of a drug dependent on?

Answer 11

Affinity - how willingly/strong the drug binds to receptor

Efficacy - ability of a drug to generate a response (by activating intracellular signalling pathways) once bound

Question 12

Define 1. full agonist and 2. partial agonist

Answer 12

1. An agonist the that generates a maximum response
2. An agonist that generates a less than maximum response
   (antagonist activity)

Question 13

What is selectivity?

Answer 13

The preference of a drug to bind to certain receptors

Question 14

What is the difference between high and low affinity full agonists?

Answer 14

Full agonists with lower affinity can still generate a maximum response but requires a higher dose than that with higher affinity

Question 15

What are the two types of receptor antagonist

Answer 15

Competitive - Binds at the same site as agonist, surmountable, shifts D-R curve to the right
Irreversible - Binds tightly or at an allosteric site, unsurmountable