Drug Absorption Flashcards

1
Q

What is pharmaceutical process?

A

Getting the drug into the patient

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2
Q

What is pharmacokinetic process?

A

Getting the drug to the site of action

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3
Q

What is pharmacodynamics process?

A

Producing the correct pharmacological effect

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4
Q

What is therapeutic process?

A

Producing the correct therapeutic effect

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5
Q

What are the 4 basic factors that determine pharmacokinetics?

A

Absorption

Distribution

Metabolism

Elimination

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6
Q

A knowledge of the factors of pharmacokinetics enables an understanding of what?

A

Dosage

Drug administration

Drug handling

Patient variability

Potential for harm

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7
Q

What must most drugs do to have biological action?

A

Enter the blood stream and be distributed to a site of action

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8
Q

What are different methods of administration?

A

Oral

Intra-venous (IV)

Subcutaneous (applied under the skin)

Intramuscular

Other GI (sublingual, rectal)

Inhalation

Nasal

Transdermal (delivered across the skin)

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9
Q

What is absorption?

A

Process of movement of unchanged drug from the site of adminstration to the systematic circulation

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10
Q

What does absorption depend on?

A

Properties of the drug

Dosage used

Anatomy and physiology of the drug absorption site

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11
Q

What is the relationship between plasma concentration and the therapeutic response?

A

There is a correlation between the two

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12
Q

What is Cmax?

A

The peak concentration

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13
Q

What is T max?

A

The time to peak concentration

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14
Q

What does the area under the curve of a concentration/time graph represent?

A

Total amount of drug that reaches systematic circulation

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15
Q

What does Tmax tell us?

A

How quickly the drug is going to get into our circulation to produce an effect

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16
Q

What does Cmax tell us?

A

Whether the effect of a drug may be toxic or ineffective

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17
Q

What does increasing the dose do in relation to Tmax and Cmax?

A

Does not increase Tmax but increases Cmax

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18
Q

What is the therapeutic range?

A

The range of concentration that a drug is active

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19
Q

What happens above the therapeutic range?

A

The drug is toxic

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20
Q

What happens below the therapeutic range?

A

The drug is ineffective

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21
Q

What is bioavailability?

A

The amount of a drug that gets into circulation and is available for biological activity

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22
Q

What is the bioavailablity of a drug given intra-venously?

A

100% bioavailability

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23
Q

How is bioavailability determined?

A

By giving the drug and working out the toal amount over time then comparing this to the IV route

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24
Q

What are some factors that affect bioavaiability?

A

Formulation

Ability of drug to pass physical barriers

Gastrointestinal effects

First pass metabolism

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25
Q

What impacts a drugs ability to cross physical barriers?

A

Particle size

Lipid solubility

pH and ionisation

26
Q

What must a drug be to dissolve in lipids?

A

Unionised

27
Q

What does first pass metabolism refer to?

A

Removal of the drug by the liver

28
Q

What is bioavailability used to work out?

A

The best dosage of a drug for the desired effect

29
Q

What are different kinds of transport across physical barriers?

A

Passive diffusion

Filtration

Bulk flow

Active transport

Facilitated transport

Ion-pair transport

Endocytosis

30
Q

What does the degree of ionisation depend on for a drug and why?

A

The environment because most drugs are weak acids or bases

31
Q

When does an unionised drug stop crossing a membrane?

A

Once equilbrium is reached

32
Q

What may happen whilst a drug is in the middle of crossing a membrane?

A

Ion trapping

33
Q

What is ion trapping?

A

Drug crosses the first membrane but then is ionised and cannot cross the second

34
Q

Where do acidic drugs get stick?

A

In compartments with a high pH

35
Q

What is the ability of a drug to diffuse across a lipid barrier expressed as?

A

Lipid-water partition coefficient

36
Q

What must a drug be to diffuse across a lipid membrane?

A

In solution

Lipid soluble

37
Q

What is the lipid-water partition coefficient?

A

Ratio of the amount of drug which dissolves in the lipid an water phase when they are in contact

38
Q

How are drugs given that cannot diffuse across lipid membranes?

A

By IV to skip most of these barriers

39
Q

Where does passive diffusion occur?

A

Along concentration gradients (requires no energy)

40
Q

What does passive diffusion depend on?

A

Lipid solubility

Degree of ionisation

41
Q

Where does facilitated diffusion occur?

A

Along the concentration gradient but requires carriers

42
Q

What are examples of things that use facilitated diffusion?

A

Monosaccharides

Amino acids

Vitamins

43
Q

Where does active transport occur?

A

Against concentration gradients (requires energy)

44
Q

What are examples of things that use active transport?

A

Ions such as K, Na and Ca

45
Q

Where does filtration occur?

A

Through channels in the cell membrane

46
Q

What is the driving force of filtration?

A

Hydrostatic pressure or osmotic pressure difference across the membrane

47
Q

What uses filtration?

A

Urea

48
Q

What are gastrointestinal factors that affect drug absorption?

A

Motility (speed of gastric absorption)

Food (can enhance or impair absorption)

Illness (can increase or decrease absorption)

49
Q

Where are most drugs absorbed?

A

Small intestine

50
Q

What is first pass metabolism?

A

Metabolism of drug prior to reaching systematic cirulation

51
Q

What are some places involved in first pass metabolism?

A

Gut lumen (acid, enzymes)

Gut wall (metabolic enzymes)

Liver (hepatic enzymes)

52
Q

What does absorption from subcutaneous/intramuscular sites depend on?

A

The blood flow at these sites

53
Q

What do drugs given subcutaneously or intramuscularly avoid?

A

First pass metabolism

54
Q

What do sublingual drugs avoid?

A

First pass metabolism

55
Q

What is sublingual?

A

Under the tongue

56
Q

What do drugs given via the rectum bypass?

A

First pass metabolism

57
Q

What is the absorption of a drug from the rectum like?

A

Slow

58
Q

What kinds of drugs are often given via the rectum?

A

Ones that cause irriation to the stomach

59
Q

What is inhalation best for?

A

Volatile agents

60
Q

How much of an inhalation drug is absorbed?

A

5-10%

61
Q

What are the advantages of transdermal drugs?

A

Avoids first pass metabolism and can provide a controlled release

62
Q

What should be considered when deciding the mode of administration?

A

Purpose and site of drug action

Disease effects

Patients ability to take medicine

Speed of action

Reliability of absorption