FoM:L2 - How do drugs work?

Question 1

What are agonists?

Answer 1

Designed to evoke a response

Question 2

When would an agonist be used?

Answer 2

disease of insufficiency

Question 3

When would an antagonist be used?

Answer 3

disease of excess

Question 4

What are the 2 types of antagonists?

Answer 4

competitive and non-competitive

Question 5

What is a reversible antagonists?

Answer 5

• does not produce a biological effect directly, but competes with an agonist for binding to the receptor
• affinity but no efficacy
• no change on maximum response

Question 6

What determines the relative antagonism?

Answer 6

relative amounts of agonist and antagonist

Question 7

What are non-competitive antagonists?

Answer 7

• irreversible
• as reactive groups on drugs form covalent bonds with receptors
• some bind allosterically

Question 8

What is the impact of non-competitive antagonists on the log-dose response curve?

Answer 8

• reduces max response of agonist
• reduces potency and efficacy

Question 9

How long do irreversible antagonists last?

Answer 9

when receptor is replaced or recycled

Question 10

What is pharmacological antagonism?

Answer 10

• antagonist acts at the same target receptor as the agonist
• competitive or non-competitive

Question 11

What is pharmacokinetic antagonism?

Answer 11

• drug interaction
• antagonist reduces [agonist] in the body
• reducing absorption or distribution
• increasing metabolism or excretion

Question 12

What is physiological antagonism?

Answer 12

2 drugs or substances which have opposing physiological actions acting by different receptors

Question 13

How could an antagonist be used to increase heart rate?

Answer 13

• antagonist for the M2 receptor
• reduces potency of ACh
• prevents heart rate being slowed

Question 14

How could an agonist be used to increase HR?

Answer 14

• adrenaline acts on B1 receptors
• agonist would increase HR

Question 15

What are spare receptors and why are they needed?

Answer 15

• receptors that are not activated when a full agonist produces a maximal response
• spare receptors increase speed of response

Question 16

What are partial agonists?

Answer 16

even if 100% of receptors are occupied by the agonist, there is never a maximum response. Low efficacy.

Question 17

Describe how a partial agonist may act as an agonist and antagonist…

Answer 17

• on its own, acts as a weak agonist
• in the presence of a full agonist, it becomes a weak antagonist as it competes with full agonist for receptors

Question 18

What are 3 non-receptor drug targets?

Answer 18

• ion channels; agonist or antagonist
• enzymes; inducer, inhibitor, pro-drug and false substrate
• transporters; allosteric, false substrate, bind to carrier site

Question 19

What is tolerance?

Answer 19

upon repeated administration of some drugs, increasing doses need to be given to achieve the same effect
fast: tachyphylaxis slow: tolerance