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BIOM2402 > Drug Disposition > Flashcards

Drug Disposition Flashcards

Module 2

1
Q

ADME:

A

Absorption
Distribution
Metabolism
Excretion

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2
Q

Entral:

A

Absorption through the GI tract

  • Oral
  • Rectal
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3
Q

Parenteral:

A

All other routes; injections, sublingual, inhalation, topical

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4
Q

The rate of diffusion is dependant on:

A

Surface area of membrane

Concentration gradient

Partition coefficient

Diffusion coefficient

Thickness of membrane

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5
Q

Rate of diffusion = (D.R.A.DC) / Dx

A

(D.R.A.DC) / Dx

Surface area of membrane (A)

Concentration gradient (DC)

Partition coefficient (R)

Diffusion coefficient (D)

Thickness of membrane (Dx)

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6
Q

Bulk flow:

A

In the bloodstream, lymphatics, or CSF

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7
Q

Diffusion:

A

Molecule-by-molecule, over a short distance

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8
Q

Chemical nature impacts diffusion. T/F

A

False. Makes no difference

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9
Q

There are four main ways by which small molecules cross cell membranes:

A
  1. Diffusing directly through the lipid
  2. Combining with a solute carrier (SLC) or other membrane transporter
  3. Diffusing through aqueous pores formed by special proteins (aquaporins) that traverse the lipid
  4. Pinocytosis.
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10
Q

Non-polar molecules dissolve freely through lipids, through to the cell membrane. T/F

A

True

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11
Q

Many acids are weak acids/bases, and exist ____

A

In both ionised and unionised states

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12
Q

Ionised compounds:

A

Cannot cross cell membrane

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13
Q

Unionised compounds:

A

Can cross cell membrane

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14
Q

Body compartments ____ reach equillibrium

A

Rarely

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15
Q

To pass endothelial barriers:

A

Molecules must transverse >2 cells to pass from one-side-to-another

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16
Q

Gaps within endothelial cells are packaged with ____

A

Filter proteins

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17
Q

Vascular endothelium separates:

A

Intra-vascular form extra-vascular

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18
Q

An unbound drug is pharmacologically active. T/F

A

True

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19
Q

The amount of drug that is bound to a protein depends on:

A
  • Conc. of free drug
  • Affinity for binding site
  • Conc. of protein
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20
Q

If a drug is absorbed within 30 minutes, it will have a ____ plasma concentration as oppose to being absorbed over several hours

A

Higher

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21
Q

Strong bases are poorly absorbed. T/F

A

True

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22
Q

Aspirin, a weak acid, is un-ionised at a low pH –> predominant absorption at the stomach; but why does it get absorbed within the small intestine?

A

The stomach lacks microvilli and its comparatively small to the small intestine.

A larger surface area and microvilli makes the small intestine a more convenient site of absorption

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23
Q

At peak plasma level:

A

The rate of absorption is equal to rate of metabolism and excretion

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24
Q

Oral administration of drugs is convenient because…

However….

A

75% is absorbed within the first 1 - 3hrs

Some drugs are not well absorbed, and may irritate gastric lining

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25
Q

Rectal administration avoids…

A

First-pass metabolism

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26
Q

A disadvantage of i.v. administration is…

A

Some drugs are toxic in high quantities. Once you inject a drug, you cant get it out of the bloodstream

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27
Q

Drugs administered via i.v. are digested within the GIT. T/F

A

False. I.v. is parentral

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28
Q

The optimal administration for emergencies is via:

A

i.v.

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29
Q

Sub-cutaneous injections extends…

A

Time of pharmacological effect

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30
Q

S.c. administration must be administered with…

A

Oily solutions

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31
Q

Drugs administered via s.c. are vasoconstrictors only. T/F

A

True

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32
Q

Intramuscular injection increases…

A

Perfusion to the muscles

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33
Q

Hormone injections are administered through:

A

i.m.

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34
Q

The epidural for childbirth is administered via:

A

Intrathecal (i.t.)

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35
Q

Inhaling of drugs is effective due to the…

A

Thin diffusion barrier

36
Q

Sublingual absorption is useful because….

A

The tongue is highly vascularised

37
Q

Topical injections penetrate the skin rapidly. T/F

A

True

38
Q

Topical injections require ____ doses

A

Lower

39
Q

Following oral administration, the expected major pathway of absorption would be….

A

The small intestine

40
Q

Passive re-absorption primarily occurs at the:

A

Distal tubule

41
Q

Strong acids and strong bases are absorbed well. T/F

A

False.

Strong acids and strong bases are poorly absorbed

42
Q

Once within the plasma, a drug travels…

A
  1. Plasma
  2. Bulk-flow
  3. Lymph
    ___BBB___
  4. CSF
43
Q

Atropine and opiates reduce GI absorption because they…

A

Inhibit gastric emptying

44
Q

Plasma concentration is directly proportional to the drive across components. T/F

A

True

45
Q

Equilibrium =

A

K1 * cPlasma = K2 *cTtissue

46
Q

Values of K1 and K2 are determined by…

A
  • Blood flow
  • Tissue volume
  • Lipophilicity
  • Ionisation
  • Plasma + Tissue barriers
47
Q

____ drugs are available to diffuse through peripheral tissue

A

Unbound

48
Q

Drug binding is a saturable process, such that…

A

The fraction of unbound-drug in the plasma can change with concentration

49
Q

Because drugs compete for plasma binding….

A

One drug can displace a second –> Incr. free concentration

50
Q

Protein binding acts as a drug reservoir, and gives…

A

Incr. Half-life

Incr. Protein binding

51
Q

Elderly people may require a lower dosage of medication because…

A

They produce less plasma proteins –> less absorption

52
Q

Protein binding is inversely proportional to the distribution into the tissues. T/F

A

True. Diazepam has a 99% affinity for protein binding, and very poor tissue distribution

53
Q

Ethanol is…

A

Always unionised
Polar
Lipophillic
Gives a large area for distribution

54
Q

Ion trapping is described by…

A

Acidic drugs accumulating in a basic environment

Basic drugs accumulate in an acidic environment

55
Q

Drugs partitioning into adipose tissue gives…

A
  • Non-polar environment
  • Accumulation of lipophillic drugs
  • Reservoir for slow release
56
Q

Drugs crossing the BBB must be…

A
  • Small
  • Lipophillic
  • Substrate for specific transporters
57
Q

Most drugs leaving the body must be…

A
  • Uncharged

- Polar

58
Q

Phase l enzymatic reactions:

A

Catabolic
Incr. chemical reactivity
–> May also incr. toxicity

59
Q

Phase ll enzymatic reactions:

A 
Anabolic
Add water-soluble moiety to a drug:
- Glucuronyl
- Sulfate
- Acetyl
- Methyl
60
Q

P450 uses…

A

Fe3+ at active site

- mostly in ER

61
Q

P450 enzymes are essential for…

A

Metabolism of drugs

62
Q

P450 enzymes can be induced or inhibited by drugs. T/F

A

True

63
Q

P450 enzymes are…

A

Bound to membranes within a cell (cyto) and

Contain a heme pigment (chrome and P) that absorbs light at a wavelength of 450 nm when exposed to carbon monoxide

64
Q

Inhibition is CYP enzymes occurs when…

A

2 drugs are metabolised by the same p450 enzyme

65
Q

Phase ll reactions occur within the…

A
  • Liver
  • Lungs
  • Kidneys
66
Q

Bioavaliability =

A

Fraction of drug that reaches systemic circulation

67
Q

Organic cation transporters are involved in….

A

Passive reabsorbtion

68
Q

Organic anion transporters are involved in

A

Active reabsorbtion

69
Q

Drugs are filtered into the urine at the…

A

Bowmans capsule

70
Q

Active secretion of drugs is at the…

A

Proximal tubule

71
Q

Water is reabsorbed in the…

A

Loop of Henle

72
Q

Passive reabsorbtion of drugs is at the…

A

Collecting duct

Distal tubule

73
Q

Only unbound drugs are filtered at the glomerulus. T/F

A

True

74
Q

Renal failure may prolong drug half-life. T/F

A

True

75
Q

There is substantial absorption at a pH of 5 as oppose to…

A

pH of 8

76
Q

If the drugs are excreted into the bile?

A

Drugs appearing in bile will enter the intestines and may be reabsorbed resulting in enterohepatic circulation

77
Q

enterohepatic circulation

A

Reabsorbed across the intestinal mucosa and returned to the liver via portal circulation

78
Q

HW eq:

A

1 = A2 + 2Aa + a2

79
Q

Autosomal Dominant

A

One allele dominates such that the phenotype is the same in AA OR Aa individuals

80
Q

Autosomal Recessive

A

The phenotype is only present if both alleles are present (must be homozygote; AA or aa).

81
Q

X-Linked Recessive

A

Phenotype only occurs on the X-chromosome.

82
Q

Autosomal Co-dominant

A

Phenotype is the average of each allele.

83
Q

NAT2 is within the…

A

Liver and responsible for most drug acetylation

84
Q

Within pharmacogenetics, inter-variability may result in…

A
  • Lack of efficacy

- Unexpected harmful effects

85
Q

It is common for drugs to have a prolonged effect within babies and the elderly. Why is this?

A

Drug elimination is less efficient at these ages.

86
Q

Can morphine be used during pregnancy?

A

No. Morphine is not used as an analgesic in labour, because drug transferred
via the placenta has a long half-life in the newborn baby
and can cause prolonged respiratory depression.

87
Q

Half-life determines the time course of drug accumulation

during repeated dosing. T/F

A

True

BIOM2402 (4 decks)

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