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Pharmacology > Principles of pharmacokinetics > Flashcards

Principles of pharmacokinetics Flashcards

1
Q

Processes involved in pharmacokinetics

A

Absorption
Distribution
Metabolism
Elimination

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2
Q

Effect of enteric coating on a tablet on its rate of absorption

A

Slows

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3
Q

pKa of a drug

A

pH at which half of the drug is in its ionised form

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4
Q

Aspect of drug metabolism where the drug when taken orally is partially metabolised by liver and gut mucosa and so the concentration is reduced before it reaches systemic circulation

A

First pass metabolism

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5
Q

Mechanisms of absorption of drugs from the GI tract

A

Active transport
Passive diffusion
Pore filtration

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6
Q

Drug absorption of hydrophilic vs. hydrophobic drugs

A

Hydrophobic drugs are absorbed better

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7
Q

Site in the GI tract where most absorption takes place

A

Small intestine

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8
Q

Reverse transporter which actively pumps the dug into the gut lumen from the gut cells and reduces its absorption

A

P-glycoprotein

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9
Q

Effect of grapefruit juice on P-glycoprotein and drug concentrations

A

Inhibits P-glycoprotein and increases absorption of certain medications

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10
Q

Time frame for absorption of drugs administered IM

A

Over 10-30 minutes

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11
Q

Method of administration for most rapid drug absorption

A

IV

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12
Q

Percentage bioavailability with IV administration of a drug

A

100%

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13
Q

Two types of diffusion which can be involved in drug permeation

A

Simple diffusion

Facilitated diffusion

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14
Q

Type of diffusion where permeation takes place passively along a concentration gradient

A

Simple diffusion

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15
Q

Type of diffusion where permeation takes place along a concentration gradient but helped by the presence of carrier mechanisms

A

Facilitated diffusion

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16
Q

Type of permeation where a drug is transported against a concentration gradient, requiring energy expenditure

A

Active transport

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17
Q

Form of a drug in terms of ionisation which can cross the lipid membranes of a cell

A

Nonionised form

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18
Q

Main plasma protein that binds to acidic drugs

A

Albumin

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19
Q

Main plasma protein that binds to alkaline drugs

A

Alpha1-acid glycoprotein

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20
Q

Drugs which have 95-99% protein binding

A

Diazepam
Chlorpromazine
Amitriptyline
Imipramine

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21
Q

Drugs which have 90-95% protein binding

A

Phenytoin
Valproate
Clomipramine

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22
Q

Equation for volume of distribution

A

Volume of distribution = quantity of drug / plasma concentration at the time of administration

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23
Q

Characteristics of a drug the volume of distribution gives information about

A

If the volume of distribution is high the drug has a high affinity for tissues outside the body water and high lipid solubility
If the drug is highly protein bound its volume of distribution will be low

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24
Q

Junctions found in the blood brain barrier

A

Tight junctions

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25
Q

Definition of bioavailability

A

The percentage of a drug which is detected in the systemic circulation after its administration

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26
Q

Percentage of first pass metabolism the rectal route avoids

A

66%

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27
Q

Physiological changes in elderly people that can affect drug absorption - generally leading to same amount of drug absorption but at a slower rate

A

Reduced gastric acid secretion
Reduced gastric motility
Reduced small bowel surface area
Reduced first pass metabolism

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28
Q

Physiological changes in elderly people that can affect drug distribution

A 
Increased proportion of body fat
Decreased lean body mass
Decreased total body water
Increased alpha-1-acid glycoprotein levels
Decreased albumin levels
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29
Q

Physiological changes in elderly people that can affect drug metabolism

A

Decreased hepatic blood flow and cytochrome p450 enzyme activity - but only after age 80

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30
Q

Physiological changes in elderly people that can affect drug excretion

A

Decreased renal function

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31
Q

Solubility of drugs which are the most rapidly absorbed

A

Lipid soluble

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32
Q

Permeation of a drug

A

Lipid membrane permeability of the drug

32
Q

Permeation of a drug

A

Lipid membrane permeability of the drug

33
Q

Form of a drug which is able to cross lipid membranes of a cell

A

Ionised form

34
Q

Part of a drug - protein bound vs. not bound - which is active

A

Not protein bound

35
Q

Reversibility of plasma protein binding of drugs

A

Reversible

36
Q

Effect of protein displacement on drugs

A

Increases the plasma concentration of free drug

37
Q

Reason why protein displacement is not usually clinically significant

A

The metabolism of the drug increases in parallel with the free drug concentration

38
Q

Factors which affect the ability of a drug to cross the blood brain barrier

A

Molecule size
Lipid solubility
Ionic status

39
Q

Ionisation of molecules that are easily able to cross the blood brain barrier

A

Unionised molecules

40
Q

Name for the areas of the brain which lack a blood brain barrier

A

Circumventricular organs

41
Q

Circumventricular organs of the brain

A 
Subfornical organ
Area postrema
Vascular organ of lamina terminalis
Median eminence
Pineal gland
Part of the pituitary gland
42
Q

Administration method of a drug which theoretically allows it to cross the blood brain barrier

A

Nasal

43
Q

Measure of comparability of plasma levels of two different formulations of a drug given at the same dose and by the same route

A

Bioequivalence

44
Q

Mechanism by which a foreign agent is metabolised and eliminated

A

Xenobiotics

45
Q

Principle site of drug metabolism

A

Liver

46
Q

Four major routes of drug metabolism

A

Oxidation
Reduction
Hydrolysis
Conjugation

47
Q

Number of phases of drug metabolism

A

2

48
Q

Metabolic routes involved in phase 1 metabolism

A

Oxidation
Reduction
Hydrolysis

49
Q

Necessity of going through phase 1 metabolism to reach phase 2

A

Not necessary in all drugs

50
Q

Metabolic route involved in phase 2 metabolism

A

Conjugation

51
Q

Most common biochemical process in phase 1 metabolism

A

Oxidation

52
Q

Attachment of a hydrophilic ionised group to a drug

A

Conjugation

53
Q

Most common substance involved in conjugation

A

Glucuronic acid

54
Q

Groups added in conjugation

A 
Glucuronic acid
Sulphate
Amino acids
Acetate
Methyl
55
Q

Relative molecular mass under which a metabolised drug can be excreted in the urine

A

<300

56
Q

Relative molecular mass above which a metabolised drug must be excreted in the bile

A

> 300

57
Q

Outcomes of metabolism

A

Active drug is metabolised into an inactive metabolite ready to be excreted
Inactive prodrug is metabolised into its active drug

58
Q

Elimination occurs at a constant rate despite the concentration of the drug

A

Zero order kinetics

Has no constant half life as half life decreases with decreasing concentrations of the drug

59
Q

Elimination occurs at a proportional rate to the concentration of the drug - a constant fraction of the drug is eliminated per unit of time

A

First order kinetics

60
Q

Most drugs follow ___ order kinetics

A

First

61
Q

Substances which follow zero order kinetics

A

Phenytoin
Ethanol
Slow release preparations of drugs
Depot medication

62
Q

Patient factors affecting drug excretion

A

Increased age decreases excretion
Reduction in renal blood flow e.g. due to dehydration decreases excretion
Renal impairment decreases excretion

63
Q

Volume of plasma cleared of a drug over a specified time period - includes metabolism to an inactive metabolite and excretion

A

Clearance

64
Q

Drugs which show renal elimination without significant hepatic metabolism

A 
Lithium
Amisulpride
Sulpride
Gabapentin
Acamprosate
Amantadine
65
Q

Time taken for the plasma concentration of a drug to half

A

Half life

66
Q

Dose of a drug at which 50% of people experience a specific adverse effect

A

Median toxic dose

67
Q

Dose of a drug at which 50% of patients experience a specific therapeutic effect

A

Median effective dose

68
Q

Ratio of the median toxic dose to the median therapeutic dose

A

Therapeutic index

69
Q

Plasma levels within which the efficacy of a drug is optimum without toxicity

A

Therapeutic index range

70
Q

Plasma levels within which a drug appears to have therapeutic efficacy - does not take into account toxicity

A

Therapeutic window

71
Q

Pharmacokinetic changes in pregnancy

A 
Delayed gastric emptying
Decreased gastrointestinal motility
Increased volume of distribution
Decreased albumin level
Induction of liver metabolism
Increased GFR and renal clearance
72
Q

Trimester in which physiological changes in pregnancy are most pronounced

A

Third

73
Q

Change to plasma volume during pregnancy

A

Increases

74
Q

Cause of delayed gastric emptying in pregnancy

A

Increased progesterone levels

75
Q

Condition under which protein binding interactions of drugs become significant

A

Renal disease - can cause proteinuria

76
Q

Part of the GI tract with poor oral absorption for most psychotropics

A

Stomach

77
Q

Parts of the body where drug metabolism occurs

A

Liver
Kidneys
Intestine
Lungs

Pharmacology (34 decks)

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