Pharmacodynamics Flashcards

1
Q

What is molarity?

A

Molar concentration, also called molarity, amount concentration or substance concentration, is a measure of the concentration of a solute in a solution, or of any chemical species, in terms of amount of substance in a given volume: Molarity (M) = g/L / MWt

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2
Q

What is a ligand?

A

molecules that binds specifically to a receptor. Have intrinsic efficacy (can active receptor) have efficacy (cause a measurable response)

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3
Q

Describe affinity

A

to bind a receptor a ligand must have affinity for receptor, measure of strength of binding – higher affinity = stronger binding, high affinity allows binding at low conc

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4
Q

What is efficacy/intrinsic activity?

A

ability of the ligand to cause a response – governed by intrinsic efficacy

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5
Q

What is the name given to something that binds and activates a receptor?

A

agonist

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6
Q

How is potency defined?

A

effective conc giving 50% maximal response, depends on affinity and intrinsic efficacy. Potency = affinity + intrinsic efficacy

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7
Q

Describe what a partial agonist is

A

all receptors occupied but insufficient intrinsic efficiency for maximal response = lower intrinsic activity as they have lower efficacy then full agonists. Allows more controlled response. Work in absence or low levels of ligand. E.g. buprenorphine – higher affinity = lower Kd, but lower efficacy (no full response) more morphine

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8
Q

What is intrinsic efficacy?

A

ability to change the receptors shape making it active

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9
Q

What binds but does not activate a receptor?

A

Antagonist = binds but doesn’t activate receptor = no conformation change = no interaction with effector. Drug blocks the binding of an endogenous agonist

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10
Q

What is functional antagonism?

A

act at a completely separate receptor, initiating effects that are functionally the opposite of the agonist

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11
Q

What is reversible competitive antagonism?

A

compete with agonists for binding – inhibition is surmountable

Commonest, greater [antagonist] = great inhibition, relies on dynamic equilibrium between ligand and receptors. Cause a parallel shift to the right of the agonist conc-response curve

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12
Q

Outline irreversible competitive antagonism

A

occurs when the antagonist dissociates slowly or not at all – binds with such high affinity or change shape of receptor that another agonist will never bind = non-surmountable

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13
Q

What is non-competitive antagonism?

A

binds orthosteric site (not active site)

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14
Q

How can we measure drug-receptor interaction?

A

binding a radioactively labelled ligand, measure amount present

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15
Q

What is Bmax and Kd?

A

Bmax = max binding capacity – information about receptor number.

Kd = 50% receptor occupancy = measure of affinity, LOWER VALUE = HIGHER AFFINITY

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16
Q

Outline Emax and EC50?

A

Emax = drug conc needed for 100% response.

EC50 = POTENCY = conc giving 50% maximal response

17
Q

What is IC50?

A

[antagonist] giving 50% inhibition, measure of antagonist potency

18
Q

Define conc vs dose

A

Concentration = known concentration of a drug at site of action. Dose = conc at site of action unknown

19
Q

What is a spare receptor and why does it exist?

A

don’t need 100% receptor occupancy to achieve 100% response.

increase sensitivity = receptors can be deactivated, spare will enable quicker binding

20
Q

When is receptor number altered?

A

Increases with low activity (up-regulation). Decreases with high activity (down-regulation) for drugs this can contribute to tolerance/tachyphylaxis

21
Q

What unit is used to measure [drug]?

A

molarity