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MODULE 4 - Infectious Agents > PHARMACOLOGY > Flashcards

PHARMACOLOGY Flashcards

1
Q

What does ADME stand for?

A

Absorption
Distribution
Metabolism
Excretion

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2
Q

What is volume of distribution?

A

The fluid in which a drug seems to be dissolved

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3
Q

What is the calculation used to calculate the volume of distribution?

A

Vd = Total mass of drug in the body / Concentration of the drug in the plasma

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4
Q

What is indicated if a drug has a Vd value greater than 1 litre/kg?

A

Indicates the drug is accumulating in other body compartments (e.g. fat)

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5
Q

Which Vd value indicates a drug has distributed within the plasma?

A

0.05 litres/kg

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6
Q

Which Vd value indicates a drug has distributed into the extracellular fluid?

A

0.2 litres/kg

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7
Q

Which Vd value indicates a drug has distributed into the total body water (tissues etc.)?

A

0.55 litres/kg

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8
Q

When would a loading dose of a drug be required?

A

A loading dose is used for drugs which have a high Vd value

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9
Q

What is the calculation used to calculate the loading dose of a drug?

A

Loading dose = Vd x Ceff

Ceff = effective plasma concentration

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10
Q

List three factors that can affect the volume of distribution of a drug

A

Species
Age
Disease

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11
Q

What is the purpose of drug metabolism?

A

To increase the water solubility of the drug

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12
Q

What are the two phases of drug metabolism?

A

Phase 1 (functionalisation)
Phase 2 (conjugation)

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13
Q

Describe what happens when a drug undergoes phase 1 (functionalisation) metabolism

A

The drug is functionalised into a derivative via the exposure of a functional group

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14
Q

Describe what happens when a drug undergoes phase 2 (conjugation) metabolism

A

The drug is conjugated into an inactive conjugate via the addition of a large polar side chain to the exposed functional group

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15
Q

List the four possible reactions that a drug can undergo during phase 1 (functionalisation) metabolism

A

Oxidation
Reduction
Hydrolysis
Hydration

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16
Q

Which group of enzymes are responsible for drug metabolism?

A

Microsomal enzymes

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17
Q

Which specific group of enzymes are involved in phase 1 (functionalisation) metabolism?

A

Cytochrome P450 enzymes

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18
Q

What is presystemic metabolism?

A

When the liver or gut wall metabolises the drug before it reaches the systemic circulation

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19
Q

What are some of the consequences of presystemic metabolism?

A

Poor bioavailability
Larger drug dose needed

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20
Q

What are the possible consequences of drug induced synthesis of microsomal enzymes?

A

Increased metabolism which can cause either an increase or decrease in toxicity depending on the nature of the produced derivative

21
Q

List three examples of drugs which induce the synthesis of microsomal enzymes

A

Phenobarbitone
Rifampicin
Ethanol

22
Q

Can drug induced synthesis of microsomal enzymes affect the metabolism of other drugs as well?

A

YES

23
Q

List five factors that can affect drug metabolism

A

Previous drug therapy
Age
Disease
Species
Inter-individual variation

24
Q

What is clearance?

A

The efficiency of the irreversible elimination of a drug from the systemic circulation

25
Q

What is enterohepatic circulation?

A

The circulation between the small intestine and the liver used to recycle compounds

26
Q

Which type of kinetics do most drugs exhibit in practice?

A

First order kinetics
- Drug concentration declines exponentially with time

27
Q

K(abs)

A

Rate constant for absorption

28
Q

K(exc)

A

Rate constant fot excretion

29
Q

K(met)

A

Rate constant for metabolism

30
Q

C(t)

A

Concentration at time ‘t’

31
Q

Cl(s)

A

Total clearance of the drug

32
Q

Which pharmacological concept is presented in a concentration response curve?

A

The response to a drug is ‘dose dependent’ i.e. the more drug given, the bigger the cellular response

33
Q

What is the EC50 of a drug and what can this value be used for?

A

The EC50 value of a drug is the concentration of the drug which generates half of the maximum response. This can be useful in drug comparison

34
Q

(T/F) There can be alterations in drug receptor activity causing alterations to the concentration response curve

A

TRUE

35
Q

What are the terms used to describe a rapid decrease in drug receptor activity?

A

Desensitisation/tachyphylaxis

36
Q

What are the terms used to describe a more gradual decrease in drug receptor activity?

A

Tolerance/refractoriness

37
Q

What is the term used to describe no drug receptor activity/resistance to drug activity?

A

Resistance

38
Q

Briefly describe how an agonist (drug) elicits a cellular response

A
  1. OCCUPATION: Drug (agonist) binds to its specific receptor via affinity forming an inactive reversible drug receptor complex
  2. ACTIVATION: Reversible drug receptor complex is activated by efficacy leading to a cellular response
39
Q

What is affinity?

A

The measure of the attraction between a drug and its receptor

40
Q

What is efficacy?

A

The ability of a ligand/drug to elicit a cellular response when bound to its receptor

41
Q

How does antagonism prevent or reduce a cellular response?

A

Antagonists have no efficacy

42
Q

Describe how competitive antagonism decreases cellular effects

A

The antagonist competes with the agonist for the receptor binding site, inhibiting the agonist from binding and thereby reducing the cellular effect. This can be reversible or irreversible

43
Q

Briefly describe how reversible competitive antagonists interact with receptors

A

Reversible competitive antagonists can bind and dissociate from the receptor and the addition of more agonists can reverse the affects of reversible competitive antagonists

44
Q

Describe the appearance or graphs displaying the relationships between reversible competitive antagonists interact and receptors

A

Parallel shift
- the addition of more agonists can reverse the effects of reversible competitive antagonists allowing maximum response to be reached

45
Q

Briefly describe how irreversible competitive inhibitors interact with receptors

A

Irreversible competitive antagonists bind and dissociate very slowly or not at all

46
Q

Describe the appearance or graphs displaying the relationships between irreversible competitive antagonists interact and receptors

A

Reduction in maximum response
- agonists are unable to bind to their receptors due to the actions of the antagonist, preventing reaching the maximum response

47
Q

How does physiological antagonism work?

A

Apposing physiological actions cancel each other out

48
Q

How does chemical antagonism work?

A

Two substances combine in solution and cancel each other out i.e. chelating agents

MODULE 4 - Infectious Agents (20 decks)

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