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BIOM2402 > Drug Disposition > Flashcards

Drug Disposition Flashcards

Module 2 (87 cards)

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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
Rectal administration avoids...
First-pass metabolism
26
A disadvantage of i.v. administration is...
Some drugs are toxic in high quantities. Once you inject a drug, you cant get it out of the bloodstream
27
Drugs administered via i.v. are digested within the GIT. T/F
False. I.v. is parentral
28
The optimal administration for emergencies is via:
i.v.
29
Sub-cutaneous injections extends...
Time of pharmacological effect
30
S.c. administration must be administered with...
Oily solutions
31
Drugs administered via s.c. are vasoconstrictors only. T/F
True
32
Intramuscular injection increases...
Perfusion to the muscles
33
Hormone injections are administered through:
i.m.
34
The epidural for childbirth is administered via:
Intrathecal (i.t.)
35
Inhaling of drugs is effective due to the...
Thin diffusion barrier
36
Sublingual absorption is useful because....
The tongue is highly vascularised
37
Topical injections penetrate the skin rapidly. T/F
True
38
Topical injections require ____ doses
Lower
39
Following oral administration, the expected major pathway of absorption would be....
The small intestine
40
Passive re-absorption primarily occurs at the:
Distal tubule
41
Strong acids and strong bases are absorbed well. T/F
False. | Strong acids and strong bases are poorly absorbed
42
Once within the plasma, a drug travels...
1. Plasma 2. Bulk-flow 3. Lymph ___BBB___ 4. CSF
43
Atropine and opiates reduce GI absorption because they...
Inhibit gastric emptying
44
Plasma concentration is directly proportional to the drive across components. T/F
True
45
Equilibrium =
K1 * cPlasma = K2 *cTtissue
46
Values of K1 and K2 are determined by...
- Blood flow - Tissue volume - Lipophilicity - Ionisation - Plasma + Tissue barriers
47
____ drugs are available to diffuse through peripheral tissue
Unbound
48
Drug binding is a saturable process, such that...
The fraction of unbound-drug in the plasma can change with concentration
49
Because drugs compete for plasma binding....
One drug can displace a second --> Incr. free concentration
50
Protein binding acts as a drug reservoir, and gives...
Incr. Half-life | Incr. Protein binding
51
Elderly people may require a lower dosage of medication because...
They produce less plasma proteins --> less absorption
52
Protein binding is inversely proportional to the distribution into the tissues. T/F
True. Diazepam has a 99% affinity for protein binding, and very poor tissue distribution
53
Ethanol is...
Always unionised Polar Lipophillic Gives a large area for distribution
54
Ion trapping is described by...
Acidic drugs accumulating in a basic environment | Basic drugs accumulate in an acidic environment
55
Drugs partitioning into adipose tissue gives...
- Non-polar environment - Accumulation of lipophillic drugs - Reservoir for slow release
56
Drugs crossing the BBB must be...
- Small - Lipophillic - Substrate for specific transporters
57
Most drugs leaving the body must be...
- Uncharged | - Polar
58
Phase l enzymatic reactions:
Catabolic Incr. chemical reactivity --> May also incr. toxicity
59
Phase ll enzymatic reactions:
``` Anabolic Add water-soluble moiety to a drug: - Glucuronyl - Sulfate - Acetyl - Methyl ```
60
P450 uses...
Fe3+ at active site | - mostly in ER
61
P450 enzymes are essential for...
Metabolism of drugs
62
P450 enzymes can be induced or inhibited by drugs. T/F
True
63
P450 enzymes are...
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
Inhibition is CYP enzymes occurs when...
2 drugs are metabolised by the same p450 enzyme
65
Phase ll reactions occur within the...
- Liver - Lungs - Kidneys
66
Bioavaliability =
Fraction of drug that reaches systemic circulation
67
Organic cation transporters are involved in....
Passive reabsorbtion
68
Organic anion transporters are involved in
Active reabsorbtion
69
Drugs are filtered into the urine at the...
Bowmans capsule
70
Active secretion of drugs is at the...
Proximal tubule
71
Water is reabsorbed in the...
Loop of Henle
72
Passive reabsorbtion of drugs is at the...
Collecting duct | Distal tubule
73
Only unbound drugs are filtered at the glomerulus. T/F
True
74
Renal failure may prolong drug half-life. T/F
True
75
There is substantial absorption at a pH of 5 as oppose to...
pH of 8
76
If the drugs are excreted into the bile?
Drugs appearing in bile will enter the intestines and may be reabsorbed resulting in enterohepatic circulation
77
enterohepatic circulation
Reabsorbed across the intestinal mucosa and returned to the liver via portal circulation
78
HW eq:
1 = A2 + 2Aa + a2
79
Autosomal Dominant
One allele dominates such that the phenotype is the same in AA OR Aa individuals
80
Autosomal Recessive
The phenotype is only present if both alleles are present (must be homozygote; AA or aa).
81
X-Linked Recessive
Phenotype only occurs on the X-chromosome.
82
Autosomal Co-dominant
Phenotype is the average of each allele.
83
NAT2 is within the...
Liver and responsible for most drug acetylation
84
Within pharmacogenetics, inter-variability may result in...
- Lack of efficacy | - Unexpected harmful effects
85
It is common for drugs to have a prolonged effect within babies and the elderly. Why is this?
Drug elimination is less efficient at these ages.
86
Can morphine be used during pregnancy?
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
Half-life determines the time course of drug accumulation | during repeated dosing. T/F
True

BIOM2402 (4 decks)

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