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Pharmacology & Toxicology > L4-Pharmacodynamics > Flashcards

L4-Pharmacodynamics Flashcards

1
Q

Define receptor.

A

A protein that is activated by agonist (found naturally in the body) to produce a physiological response and can interact with antagonists.

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2
Q

Why aren’t enzymes, carrier molecules, and ion channels not receptors?

A

Because they aren’t activated by agonists to produce a physiological response.

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3
Q

What is the agonist for the beta adrenoreceptor on heart muscle cells?

A

Adrenaline

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4
Q

What does adrenaline do to the heart muscles when it binds to the receptor?

A

Increase the heart rate and force of contraction.

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5
Q

What is the incorrect definition of a receptor?

A

The incorrect definition of a receptor is any target molecule with which a drug molecule combines to elicit a specific effect, including enzymes, carrier molecules, ion channels, and receptors.

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5
Q

How does potency relate to affinity?

A

Drugs with high potency generally have high affinity for the receptors and will occupy a significant proportion of them at lower concentrations.

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5
Q

What’s affinity?

A

Tendency of a drug to bind to the receptors.

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6
Q

What’s efficacy?

A

Tendency of a drug to activate the receptor.

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7
Q

What can contain affinity and efficacy?

A

Agonists

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8
Q

What only contains an affinity?

A

Antagonists

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9
Q

What’s potency?

A

The amount of drugs needed to produce an an effect.

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10
Q

How is drug binding experimentally determined?

A

Drug binding is determined by using a radiolabeled drug at various concentrations, which is incubated with tissue homogenate containing receptors. The amount of drug bound to receptors is measured at each concentration.

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11
Q

What does the binding curve represent?

A

The binding curve represents the relationship between drug concentration and the amount of drug bound to the receptors.

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12
Q

What is the definition of affinity (KA)?

A

Affinity (KA) is defined as the concentration of drug at which 50% of the binding sites are occupied.

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13
Q

What does the binding capacity (Bmax) represent?

A

The binding capacity (Bmax) represents the density of receptors or binding sites in the tissue. This is the maximum point at which all receptors are saturated by the drug.

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14
Q

How can the binding curve be transformed?

A

The points on the binding curve can be transformed into a straight line, where the slope is the affinity (KA) and the x-intercept is the binding capacity (Bmax).

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15
Q

What does K^+1 represent in drug binding kinetics?

A

K^+1 represents the rate at which the drug binds to the receptor.

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16
Q

What does K^-1 represent in drug binding kinetics?

A

K^-1 represents the rate at which the drug dissociates from the receptor.

17
Q

How is affinity (KA) related to binding kinetics?

A

Affinity (KA) is determined by the ratio of K^-1 (dissociation rate) to K^+1 (binding rate). A low KA indicates high affinity because the drug binds quickly (high K^+1) or dissociates slowly (low K^-1).

18
Q

Can binding measure the effect of a drug?

A

No, binding only measures the amount of drug attached to receptors. The effect of the drug is measured by the physiological response.

19
Q

What is the concentration-response curve?

A

The concentration-response curve measures the physiological effect of different concentrations of a drug. It estimates the maximum response (Emax) and the concentration that produces 50% of the maximum response (EC50 or ED50).

20
Q

What is the difference between full agonists and partial agonists?

A

Full agonists: Can produce a maximal response when binding to receptors.
Partial agonists: Can only produce a sub-maximal response even when binding to all available receptors.

21
Q

What is competitive antagonism?

A

Competitive antagonism occurs when an antagonist competes with an agonist for the same binding site on the receptor.

22
Q

Give an example of competitive antagonism.

A

An example is the competition between isoprenaline (agonist that increases heart rate) and propranolol (antagonist), which compete for binding sites on the adrenoreceptor.

23
Q

What is non-competitive antagonism?

A

Non-competitive antagonism occurs when the antagonist does not compete for the same binding site as the agonist but blocks part of the signaling chain that leads to the physiological response.

24
Q

What is receptor desensitization?

A

Receptor desensitization refers to the gradual decrease in a receptor’s responsiveness following continuous exposure to an agonist.

25
Q

How does desensitization occur in ligand-gated ion channels?

A

Desensitization in ligand-gated ion channels occurs when the channel closes despite the agonist still being bound, due to a conformational change.

26
Q

What is LD50?

A

LD50 (Median Lethal Dose) is the dose of a substance that is lethal to 50% of the tested population.

27
Q

What are the different types of toxicity?

A
  • Acute toxicity
  • Sub-acute toxicity
  • Sub-chronic toxicity
  • Chronic toxicity
28
Q

Acute toxicity

A

Results from a single exposure to a substance.

29
Q

Sub-acute toxicity

A

Results from repeated exposure over 14 days or less.

30
Q

Sub-chronic Toxicity

A

Results from repeated exposure over 90 days.

31
Q

Chronic Toxicity

A

Results from continuous exposure for more than 90 days.

32
Q

How is toxicity categorized based on LD50?

A
  • Extremely toxic
  • Highly toxic
  • Moderately toxic
  • Slightly toxic
33
Q

Extremely toxic

A

LD50 < 1 mg/kg

34
Q

Highly toxic

A

LD50 < 50 mg/kg

35
Q

Moderately toxic

A

LD50 < 500 mg/kg

36
Q

Slightly toxic

A

LD50 > 500 mg/kg

37
Q

What is the difference between hazard and toxicity?

A

Hazard: The actual risk of poisoning and includes both toxicity and potential human exposure.
Toxicity: The inherent danger of a substance, hazard can be minimized by reducing exposure.

38
Q

Binding equation

A

B = Bmax.XA /(XA + KA)
B = amount of drug bound
XA = concentration of drug
XB = affinity

39
Q

Binding equation when XA = KA

A

B = Bmax/2

40
Q

What’s another receptor desensitization type?

A
  • Receptors linked to second messengers (GPCRS) are often phosphorylated to become inactive.
  • Down regulation
41
Q

Down regulation

A

Prolonged exposure to agonists often results in a gradual decrease in the number of receptors expressed on the cell surface.

Pharmacology & Toxicology (10 decks)

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