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Foundations of Medicine JMO > Pharmacodynamics > Flashcards

Pharmacodynamics Flashcards

1
Q

What is a receptor?

A

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

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2
Q

What is a ligand?

A

A substance that is bound to a protein

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3
Q

What is affinity?

A

The tendency of a ligand to bind to its receptor

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4
Q

What is efficacy?

A

The tendency for an agonist to activate the receptor

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5
Q

What is an agonist?

A

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

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6
Q

What is an antagonist?

A

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

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7
Q

What is a drug?

A

A chemical that affects physiological function in a specific way

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8
Q

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

A

A + R —> AR (K+1)
AR —> A + R (K-1)

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9
Q

What is the relationship between concentration and rate at equilibrium?

A

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

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10
Q

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

A

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

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11
Q

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

A

[AR]
——
[Rt]

where Rt is the initial concentration of free receptors

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12
Q

What is the Hill-Langmuir equation?

A

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

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13
Q

What is the equation for the dissociation equilibrium constant?

A

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

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14
Q

What is Kd or IC50?

A

The concentration at which 50% of the receptors are occupied

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15
Q

What is a drugs MOA?

A

Its Mechanism Of Action

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16
Q

What type of drug is amitriptyline?

A

A tricyclic antidepressant

17
Q

To which receptors is amitriptyline an antagonist?

A

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

18
Q

How can amitriptyline cause drowsiness?

A

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

19
Q

How can amitriptyline cause a dry mouth?

A

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

20
Q

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

A

Signal amplification occurs

21
Q

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

A

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

22
Q

What is a partial agonist?

A

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

23
Q

Which receptor is buprenorphine a partial agonist against?

A

The µ-opioid receptor

24
Q

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

A

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

25
Q

What is the formula for concentration ratio?

A

EC50 with agonist / EC50 without agonist

26
Q

What is the concentration ratio?

A

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

27
Q

What is prazosin an antagonist against?

A

The α-adrenoceptors, allowing it to treat hypertension

28
Q

What character is used as an indication of antagonist potency?

A

pA2

29
Q

How does affinity change as Ka increases?

A

Affinity decreases as Ka increases

30
Q

How does affinity change as pKa increases?

A

Affinity increases as pKa increases

31
Q

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

A

A sigmoidal curve

32
Q

What does the Hill-Langmuir equation describe?

A

The relationship between ligand concentration and the proportion of receptors

33
Q

What is potency?

A

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

Foundations of Medicine JMO (56 decks)

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