Pharmacodynamics

Question 1

What is a receptor?

Answer 1

A class of cellular macromolecules that are concerned specifically and directly with chemical signalling

Question 2

What is a ligand?

Answer 2

A substance that is bound to a protein

Question 3

What is affinity?

Answer 3

The tendency of a ligand to bind to its receptor

Question 4

What is efficacy?

Answer 4

The tendency for an agonist to activate the receptor

Question 5

What is an agonist?

Answer 5

A ligand that binds to a receptor and alters the receptor state resulting in a biological response

Question 6

What is an antagonist?

Answer 6

A drug that reduces the action of another drug, usually an agonist. Many act on the same receptor molecule as the agonist

Question 7

What is a drug?

Answer 7

A chemical that affects physiological function in a specific way

Question 8

What equation shows the relationship between ligand concentration and receptor occupancy?

Answer 8

A + R —> AR (K+1)
AR —> A + R (K-1)

Question 9

What is the relationship between concentration and rate at equilibrium?

Answer 9

(K+1)[A][R] = (K-1)[AR]

Question 10

What is the formula for Pr (Proportion of free receptors)?

Answer 10

[R]/[Rt] where Rt is the initial concentration of free receptors

Question 11

What is the formula for Par (Proportion of bound receptors)?

Answer 11

[AR]
——
[Rt]

where Rt is the initial concentration of free receptors

Question 12

What is the Hill-Langmuir equation?

Answer 12

P(AR) = [A] / ([A] + Ka)

Question 13

What is the equation for the dissociation equilibrium constant?

Answer 13

Ka = (K-1) / (K+1)

Question 14

What is Kd or IC50?

Answer 14

The concentration at which 50% of the receptors are occupied

Question 15

What is a drugs MOA?

Answer 15

Its Mechanism Of Action

Question 16

What type of drug is amitriptyline?

Answer 16

A tricyclic antidepressant

Question 17

To which receptors is amitriptyline an antagonist?

Answer 17

Norepinephrine (Noradrenaline) Transporter (NET)
Seretonin Transporter (SERT)
Acetylcholine M1-M5 receptors (ACh)
Histamine H1 receptor

Question 18

How can amitriptyline cause drowsiness?

Answer 18

Amitriptyline acts as an antagonist to the Histamine H1 receptors in the brain when it passes the blood-brain barrier, leading to sedative effects

Question 19

How can amitriptyline cause a dry mouth?

Answer 19

Amitriptyline acts as an antagonist to the M1-M5 Acetylcholine receptors, which leads to an anti-muscarinic effect

Question 20

Why can only a few receptors need to be activated to produce a large response?

Answer 20

Signal amplification occurs

Question 21

What is the equation for the 2 state model of pharmokinetics?

Answer 21

A + R —> AR (K+1)
then
AR —> A + R (K-1)
or
AR —> AR* (Activated) (K+2)

Question 22

What is a partial agonist?

Answer 22

An agonist that, in a given tissue, cannot cause a full effect, even with 100% receptor occupancy

Question 23

Which receptor is buprenorphine a partial agonist against?

Answer 23

The µ-opioid receptor

Question 24

How does the effectiveness of an antagonist decrease as agonist concentration increases?

Answer 24

It decreases
At low agonist concentrations, the antagonist can form a blockade against the agonist so that it cannot bind to the receptor
At high agonist concentrations, the agonist can outcompete the antagonist and overcome the blockade

Question 25

What is the formula for concentration ratio?

Answer 25

EC50 with agonist / EC50 without agonist

Question 26

What is the concentration ratio?

Answer 26

The number of times greater concentration of agonist required to give 50% response with an antagonist than without

Question 27

What is prazosin an antagonist against?

Answer 27

The α-adrenoceptors, allowing it to treat hypertension

Question 28

What character is used as an indication of antagonist potency?

Answer 28

pA2

Question 29

How does affinity change as Ka increases?

Answer 29

Affinity decreases as Ka increases

Question 30

How does affinity change as pKa increases?

Answer 30

Affinity increases as pKa increases

Question 31

What shape is formed by a logarithmic plotting of the Hill-languir equation?

Answer 31

A sigmoidal curve

Question 32

What does the Hill-Langmuir equation describe?

Answer 32

The relationship between ligand concentration and the proportion of receptors

Question 33

What is potency?

Answer 33

An expression of the activity of a drug, in terms of concentration or amount needed to produce a defined effect such as EC50