8. Drugs & Receptors

Question 0

How is concentration in grams per litre calculated?

Answer 0

Molarity x molecular weight

Question 1

How is molarity calculated?

Answer 1

Grams per litre/molecular weight

Question 2

What is the binding of a receptor governed by?

Answer 2

The affinity of the ligand and receptor

Question 3

What is activation of a receptor governed by?

Answer 3

The intrinsic efficacy

Question 4

What is efficacy?

Answer 4

The cell and tissue independent factors between a ligand binding and a response

Question 5

Agonists have:
affinity and efficacy?
affinity only?
efficacy only?
none?

Answer 5

Agonists have both affinity and efficacy

Question 6

Antagonists have:
Affinity and efficacy?
Affinity only?
Efficacy only?
None?

Answer 6

Antagonists have only affinity

Question 7

How can drug receptor binding be measured?

Answer 7

Radioligands

Question 8

What is Bmax?

Answer 8

The maximum binding capacity

Question 9

What is Kd?

Answer 9

The dissociation constant, it is a measure of affinity

Measured as the concentration of drug at half max occupancy of receptors

Question 10

A high Kd means what?

Answer 10

A low affinity for the receptor

Question 11

A drug receptor binding curve on a logarithmic x axis will give you what graph shape?

Answer 11

Sigmoidal

Question 12

How do you measure the EC50 and what does it represent?

Answer 12

Effective concentration giving 50% of the max response

This shows potency which is a combination of affinity and efficacy

Question 13

Which has greater affinity for Beta 2 receptors, salbutamol or salmeterol?

Answer 13

Salmeterol

Question 14

What enhances the utility of salbutamol?

Answer 14

Inhaled directly into the lungs hence straight onto beta 2 receptors

Question 15

What is the problem with giving asthma drugs IV?

Answer 15

Salmeterol cannot be given IV, salbutamol can but has poor selectivity for beta 2 receptors, hence it agonises beta 1 as well, speeding up the heart.

Question 16

Less than 100% receptor occupancy giving a 100% response leads to what?

Answer 16

Spare receptors

Question 17

Does number of receptors have an effect on potency?

Answer 17

Yes

Question 18

What is a partial agonist?

Answer 18

A drug that cannot produce a maximal effect even with full receptor occupancy

Question 19

Can a partial agonist be more potent than a full agonist?

Answer 19

Yes as potency is dependant of affinity and efficacy

Question 20

What is buprenorphine used for?

Answer 20

Buprenorphine is a partial agonist which has higher affinity but lower efficacy than the full agonist morphine. This means it can be used to out compete morphine with less of the respiratory depression that opioids cause.

Question 21

What is IC50?

Answer 21

The concentration of antagonist that gives 50% inhibiton

Question 22

What is naloxone?

Answer 22

High affinity opioid antagonist which is used to reverse respiratory depression as it will displace other opioids

Question 23

What does the agonist response graph look like with increasing amounts of irreversible competitive antagonist?

Answer 23

Shifts it to the right as spare receptors are filled, then down as there are insufficient receptors for a full response

Question 24

What is phenoxybenzamine?

Answer 24

Irreversible alpha 1 adrenoreceptor blocker used in hypertension episodes in pheochromocytoma

Question 25

Name a non competitive antagonist used to analgesia

Answer 25

Ketamine