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Pharmacology > Pharmacokinetics > Flashcards

Pharmacokinetics Flashcards

1
Q

What is pharmacokinetics?

A

What the body does to a drug

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2
Q

What are the main components of pharmacokinetics?

A

Absorption
Distribution
Metabolism
Elimination

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3
Q

What factors affect pharmacokinetics?

A 
Bioavailability
Half-life
Drug elimination 
Intra-subject variability 
Drug-drug interactions
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4
Q

What is bioavailability?

A

Measure of drug absorption into body compartment where it can be used

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5
Q

What is the bioavailability of IV drugs?

A

100%

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6
Q

What factors affect bioavailability?

A

Absorption

  • formulation
  • age
  • food
  • vomiting
  • malabsorption

First pass metabolism

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7
Q

What is first pass metabolism?

A

Metabolism before reaching systemic circulation

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8
Q

What factors affect distribution?

A

Blood flow
Lipophilicity
Hydrophilicity
Protein binding

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9
Q

What is Vd?

A

Volume of distribution

= how widely a drug is distributed in the body

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10
Q

How is Vd calculated?

A

Dose/[drug]plasma

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11
Q

What does a small Vd show?

A

Drug confined to plasma and extracellular fluid

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12
Q

What does a large Vd show?

A

Drug distributed throughout tissues

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13
Q

How are Vd and t1/2 related?

A

t1/2 is proportional to Vd

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14
Q

What are the main routes of administration?

A

Enteral

Parenteral

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15
Q

What does enteral mean?

A

Via the GI tract

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16
Q

What are examples of enteral routes?

A

Oral
Sublingual
Rectal

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17
Q

What does parenteral mean?

A

Not via the GI tract

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18
Q

What are examples of parenteral routes?

A

IV
SC
IM

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19
Q

What is a pneumonic for drug administration?

A

Oi It is sir

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20
Q

What are the routes for drug administration?

A 
Oral
Intravenous
Intramuscular
Transdermal 
Intranasal 
Subcutaneous 
Sublingual 
Inhalation 
Rectal
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21
Q

What are the main processes of drug absorption?

A

Passive diffusion
Facilitated diffusion
Primary/secondary active transport
Pinocytosis

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22
Q

What type of drugs use passive diffusion?

A

Lipophilic drugs

Weak acids/bases

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23
Q

What type of drugs use facilitated diffusion?

A

Drugs with a net ionic charge

24
Q

What molecules are used for facilitated diffusion?

A

SLCs(solute carriers)

  • OATs (organic anion transporters)
  • OCTs (organic cation transporters)
25
What factors affect drug absorption?
``` GI length /SA Drug lipophilicity Density of SLC expression in GI tract Blood flow GI motility First pass metabolism ```
26
What is the effect of first pass metabolism?
Reduces availability of drug reaching systemic circulation
27
How is biovailability calculated?
Area under graph ([plasma] against time)
28
What are the main mechanisms of drug distribution?
Bulk flow | Diffusion
29
What factors affect drug distribution?
Lipophilicity Hydrophilicity Degree of drug binding to plasma/tissue proteins
30
How does lipophilicity affect distribution?
Lipophilic drugs can move freely across membrane barriers
31
How does hydrophilicity affect distribution?
Needs more help crossing membrane barriers Relies on - capillary permeability - local pH - presence of OAT/OCTs
32
How does drug protein binding affect distribution?
Only free drugs can bind to target sites
33
Where does most drug metabolism occur?
Liver
34
What molecules metabolise drugs?
Phase I + II enzymes
35
What carries out phase I metabolism?
Cytochrome P450 enzymes
36
What happens when drugs are metabolised?
Ionic charge is increased
37
What else does phase I metabolism do?
Activates prodrugs
38
What carries out phase II metabolism?
Hepatic enzymes
39
What happens in phase II metabolism?
Ionic charger is further increased
40
What is the effect of phase II metabolism?
Enhances renal elimination
41
What factors affect drug metabolism?
Age Sex General health CYP450 inducers/inhibitors
42
What drugs are CYP450 inducers?
``` Carbamazepine Rifampicin Barbiturates Phenytoin St John's Wort ```
43
What drugs are CYP450 inhibitors?
``` Sodium valproate Ciprofloxacin Sulphonamide Cimetidine/omeprazole Antifungals Amiodarone Isoniazid Erithromycin/clarithromycin Grapefruit juice ```
44
What is the main route of drug elimination?
Kidney
45
What are other routes of drug elimination?
``` Bile Lung Breast milk Sweat Tears Genital secretions Saliva ```
46
What are the 3 processes involved with renal excretion?
Glomerular filtration Active tubular secretion Passive tubular reabsorption
47
What happens in glomerular filtration?
Unbound drug enters tubule
48
Where does active tubular secretion occur?
PCT
49
What happens in the PCT?
High expression of OATs + OCTs Carry ionised molecules Lipophilic molecules pass back into blood
50
Where does passive tubular reabsorption occur?
DCT
51
What happens in the DCT?
Passive reabsorption of lipophilic drugs
52
What is clearance?
The volume of plasma that is completely cleared of the drug per unit time
53
How is total body clearance calculated?
Hepatic clearance + renal clearance
54
What is the unit for clearance?
ml/min
55
What is t1/2?
Half life The amount of time over which the concentration of a drug in plasma decreases to one half og the concentration when it was first measured
56
How is t1/2 calculated?
t1/2 = (0.693xVd)/Cl
57
How many half lives does it take to clear a drug?
5

Pharmacology (27 decks)

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