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Semester 2 > M&R Session 9 > Flashcards

M&R Session 9 Flashcards

0
Q

What four things does the pharmaceutical process consider?

A

Formulation
Compliance
Site of administration
Bioavailability of drug

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1
Q

What question does the pharmaceutical process consider?

A

Is drug getting into patient?

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2
Q

What is the advantage of using a specific site of administration?

A

Concentrates drug at site of action
Decreases systemic absorption
Decreases off-target effects

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3
Q

What is the bioavailability of a drug?

A

The proportion that makes it to the circulation unchanged

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4
Q

What does the bioavailability of a drug depend on?

A

1st pass effect
Gut absorption
Pharmaceutical factors

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5
Q

How is bioavailability calculated?

A

(AUC oral)/(AUC injected) x 100

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6
Q

What question does the pharmacokinetic process consider?

A

Is drug getting to site of action?

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7
Q

What is the therapeutic ratio?

A

max. tolerated dose/min. effective dose

= LD50/ED50

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8
Q

What is LD50?

A

Toxic dose in 50% of the population

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9
Q

Give an example of a drug with a small therapeutic index.

A

Warfarin

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10
Q

Give an example of a drug with a large therapeutic index.

A

Penicillin

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11
Q

What does a small therapeutic index indicate?

A

A large overdose is needed before adverse effects occur

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12
Q

What is the disadvantage of a fast release prep?

A

May be above [toxic] for a short amount of time

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13
Q

What is the disadvantage of a slow release prep?

A

May not remain in the therapeutic window for long

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14
Q

What question does the pharmacodynamic process consider?

A

Is drug producing desired effect?

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15
Q

What question does the therapeutic process consider?

A

Is this translated to a therapeutic effect?

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16
Q

What is first pass metabolism?

A

When drugs administered orally undergo oxidation and conjugation in the liver before reaching systemic circulation

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17
Q

What alternative administration routes can be used to avoid first pass metabolism?

A

Parenteral (IV, IM, SC)
Rectal
Sublingual

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18
Q

What is the volume of distribution?

A

Theoretical volume into which drug is distributed if this occurred instantaneously

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19
Q

Why do hydrophobic drugs appear to have a huge volume of distribution?

A

Absorbed by fat so don’t enter bloodstream

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20
Q

What property of a drug does the volume of distribution indicate?

A

Hydrophobicity

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21
Q

What determines the action of a drug at its receptor and its elimination?

A

Protein binding

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22
Q

What are protein binding interactions?

A

2nd hydrophobic drug binds displacing 1st and causing it to reach toxic levels

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23
Q

When are protein binding drug interactions important?

A

When object drug is:
>90% bound to albumin
Has a small volume of distribution
Has a low therapeutic ratio

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24
Q

Give two examples of object drugs and their precipitant drugs.

A

Warfarin - sulphonamides, aspirin, phenytoin

Tolbutamide - sulphonamides, aspirin

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25
Q

How low is the dose of Class I (object) drug used to keep [free drug] low?

A

A dose lower than the number of albumin binding sites

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26
Q

What doses are Class II (precipitant) drugs used at?

A

Doses higher than the number of binding sites so object drug is displaced

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27
Q

Why are drug binding interactions transient?

A

Elimination rate rises as it is dependent on free drug levels which have risen

28
Q

How quickly is a new steady state restored in brung binding interactions?

A

Within a few days

29
Q

What is first order kinetics?

A

Rate of elimination is proportional to drug level

30
Q

What is special about the half life of a drug that follows first order kinetics?

A

It is defined

31
Q

How does first order kinetics appear on a linear scale?

A

Exponential decrease

32
Q

How does first order kinetics appear on a log scale?

A

Linear

33
Q

At what drug doses are first order kinetics seen?

A

Low

34
Q

How is the therapeutic response from a dose increase of a first order kinetic drug described?

A

Predictable

35
Q

What is zero order kinetics?

A

Rate of elimination is a constant

36
Q

Why is the rate of elimination constant in zero order kinetics?

A

The reaction is saturated

37
Q

Are first or zero order kinetic drugs more long lived?

A

Zero order

38
Q

How do zero order kinetics appear on a linear scale?

A

Straight line

39
Q

At what drug doses are zero order kinetics seen?

A

High

40
Q

What happens to the therapeutic response as the elimination mechanism is saturated?

A

Suddenly escalates

41
Q

How many half lives does it take to reach a new steady state in repeated drug administration?

A

5

42
Q

Does the number of half lives needed to reach a steady state in repeated drug administration depend on dose of frequency of administration?

A

Nope

43
Q

If the half life of a drug is long and a rapid effect is desired, what kind of dose is used?

A

Loading dose

44
Q

What often determines a loading dose?

A

Volume of distribution

45
Q

What is used to top up a loading dose?

A

Maintenance doses

46
Q

Give two examples of drugs which utilise loading doses.

A

Digoxin - AF

Heparin - anticoagulation

47
Q

By what two methods can drug elimination take place?

A

Metabolism

Excretion

48
Q

Briefly describe the process of drug metabolism.

A

Enters through portal/systemic circulation –> phase I –> oxidation +/- hydrolysis –> phase II –> conjugation products

49
Q

What enzymes are used in the liver to metabolise drugs?

A

Mixed function oxidases consisting of cytochrome P450 reductase

50
Q

What property of cytochrome P450 allows it to act on a range of drugs?

A

Low substrate specificity

51
Q

What kind of drugs does P450 reductase have an affinity for?

A

Lipid soluble

52
Q

What alters P450 levels?

A

Diet/drug interaction can induce or inhibit

53
Q

When in P450 susceptible to drug interactions?

A

Low therapeutic ratio
Drug at minimum effective concentration
Zero order metabolism

54
Q

Give three examples of P450 inducers.

A

Phenoarbitone
Rifampicin
Cigarette smoke

55
Q

What determines if a drug is ionised or not when excreted by the kidney?

A

pH of filtrate

56
Q

Which moiety of drug is lipid soluble and can easily cross membrane for excretion?

A

Non-ionised

57
Q

Which fraction of the drug is filtered?

A

Free fraction

58
Q

Can drugs be actively secreted by the tubules?

A

Yes

59
Q

Give an example of a drug which can be secreted by tubules and its location of secretion.

A

Penicillin by PCT

60
Q

Which drugs are seen most rapidly in the urine?

A

Ionised, lipid-insoluble

61
Q

What does passive reabsorption depend on?

A

pH

62
Q

What effect does acid and alkaline urine have on the absorption of weak acid drugs?

A

Acid urine = increased absorption

Alkaline urine = decreased absorption

63
Q

What effect does acid and alkaline urine have in the absorption of weak bases?

A

Acid urine = decreased absorption

Alkaline urine = increased absorption

64
Q

How is aspirin poisoning treated?

A

Weak acid so forced alkaline diuresis to decrease absorption

65
Q

How should the maintenance dose of a drug with a longer half life due to kidney excretion be altered?

A

Decreased

66
Q

How does half life relate to time taken to reach steady state?

A

Longer half life = longer time to reach steady state

67
Q

In prescription in renal disease, what two things can be altered?

A

Loading dose

Protein binding

68
Q

How is protein binding altered when prescribing in renal disease?

A

Application of a co-molecule

Semester 2 (45 decks)

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