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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
Q

What factors affect drug absorption?

A 
GI length /SA
Drug lipophilicity 
Density of SLC expression in GI tract 
Blood flow 
GI motility 
First pass metabolism
26
Q

What is the effect of first pass metabolism?

A

Reduces availability of drug reaching systemic circulation

27
Q

How is biovailability calculated?

A

Area under graph ([plasma] against time)

28
Q

What are the main mechanisms of drug distribution?

A

Bulk flow

Diffusion

29
Q

What factors affect drug distribution?

A

Lipophilicity
Hydrophilicity
Degree of drug binding to plasma/tissue proteins

30
Q

How does lipophilicity affect distribution?

A

Lipophilic drugs can move freely across membrane barriers

31
Q

How does hydrophilicity affect distribution?

A

Needs more help crossing membrane barriers

Relies on

  • capillary permeability
  • local pH
  • presence of OAT/OCTs
32
Q

How does drug protein binding affect distribution?

A

Only free drugs can bind to target sites

33
Q

Where does most drug metabolism occur?

A

Liver

34
Q

What molecules metabolise drugs?

A

Phase I + II enzymes

35
Q

What carries out phase I metabolism?

A

Cytochrome P450 enzymes

36
Q

What happens when drugs are metabolised?

A

Ionic charge is increased

37
Q

What else does phase I metabolism do?

A

Activates prodrugs

38
Q

What carries out phase II metabolism?

A

Hepatic enzymes

39
Q

What happens in phase II metabolism?

A

Ionic charger is further increased

40
Q

What is the effect of phase II metabolism?

A

Enhances renal elimination

41
Q

What factors affect drug metabolism?

A

Age
Sex
General health
CYP450 inducers/inhibitors

42
Q

What drugs are CYP450 inducers?

A 
Carbamazepine
Rifampicin
Barbiturates
Phenytoin 
St John's Wort
43
Q

What drugs are CYP450 inhibitors?

A 
Sodium valproate
Ciprofloxacin 
Sulphonamide
Cimetidine/omeprazole
Antifungals
Amiodarone
Isoniazid
Erithromycin/clarithromycin 
Grapefruit juice
44
Q

What is the main route of drug elimination?

A

Kidney

45
Q

What are other routes of drug elimination?

A 
Bile
Lung 
Breast milk 
Sweat
Tears
Genital secretions
Saliva
46
Q

What are the 3 processes involved with renal excretion?

A

Glomerular filtration
Active tubular secretion
Passive tubular reabsorption

47
Q

What happens in glomerular filtration?

A

Unbound drug enters tubule

48
Q

Where does active tubular secretion occur?

A

PCT

49
Q

What happens in the PCT?

A

High expression of OATs + OCTs
Carry ionised molecules

Lipophilic molecules pass back into blood

50
Q

Where does passive tubular reabsorption occur?

A

DCT

51
Q

What happens in the DCT?

A

Passive reabsorption of lipophilic drugs

52
Q

What is clearance?

A

The volume of plasma that is completely cleared of the drug per unit time

53
Q

How is total body clearance calculated?

A

Hepatic clearance + renal clearance

54
Q

What is the unit for clearance?

A

ml/min

55
Q

What is t1/2?

A

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
Q

How is t1/2 calculated?

A

t1/2 = (0.693xVd)/Cl

57
Q

How many half lives does it take to clear a drug?

A

5

Pharmacology (27 decks)

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