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Pharmocolgy > P3: Drug Administration and Distribution > Flashcards

P3: Drug Administration and Distribution Flashcards

1
Q 
Name the 8 administration routes.
O 
I.v 
I.m/S
B 
R 
T 
I 
I.c.v
A
  • Oral (per os; p.o.)
  • Intravenous (i.v.)
  • Intramuscular (i.m.)/ Subcutaneous
  • Buccal
  • Rectal
  • Transdermal
  • Inhalation
  • Intracerebroventricular (i.c.v.) stick injection in brain
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2
Q

Advantages with Oral Administration (5)

A
  • Easy
  • No sterile preparations
  • No special skills nor apparatus
  • Convenient
  • Generally accepted by the patient
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3
Q

Problems with Oral Administration (4)

A
  • Could be altered by stomach acidity
  • Could be digested by proteolytic enzymes
  • Potential poor/no absorption
  • Potential first pass metabolism
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4
Q

What affects first-pass metabolism in regards to a metabolite?

A

Depends on whether or not the metabolite(s) is active

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5
Q

Advantages with Intravenous Administration (3)

A
  • No absorption problems (enters systemic circulation)
  • All of the dose enters the systemic circulation
  • Can be given by slow injection or infusion
  • Can be stopped if necessary
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6
Q

Problems with Intravenous Administration (2)

A
  • Needs sterile apparatus

- Certain skill required

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7
Q

Advantages with Intramuscular and Subcutaneous Administration (3)

A
  • Low skill required (insulin, s.c.)
  • Allows slower sustained release
  • Avoids problems with oral administration
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8
Q

Problems with Intramuscular and Subcutaneous Administration (2)

A
  • Sterile conditions required
  • Not suitable for all drugs because too slow (E.g. diazepam)
  • slow to reach peak conc.
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9
Q

What administration route does glyceryl trinitrate take?

What is it used for?

A
  • Sublingual, absorbed from the Buccal cavity

- Rapidly absorbed to give relief from angina

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10
Q

What is an advantage of sublingual administration route?

A

Drugs absorbed from buccal cavity do not enter the portal vein so they avoid first-pass metabolism

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11
Q

What are the benefits and reasons for using rectal administration

A

When other routes are unsuitable or for sustained action

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12
Q

What type of drugs use transdermal administration?

A

Limited to Potent, lipohillic drugs (through skin)

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13
Q

What is an advantage of inhalation as an administration route?

A

Large Surface Area

Rapid absorption and onset of affect

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14
Q

Name the 5 possible mechanisms of drug absorption

A

1) Passive diffusion
2) Filtration through channels
3) Facilitated diffusion
4) Active transport
5) Pinocytosis
(most drugs are passive)

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15
Q

What are the two major families of drug transporters?

A
  • Solute carriers (SLC)
  • ABC transporters
    (ATP-binding cassette)
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16
Q

What do ABC transporters do?

A

ABC transporters are primarily active efflux pumps

17
Q

What do SLCs do?

A
  • Gets rid of waste and carries out nutrient transport
  • Drugs can hijack them
  • Use active transport and facilitated diffusion
    (second largest category of membrane proteins after GPCRs)
18
Q

What are the 4 things that transport across membranes depend on?

A
  • Lipophilicity
  • Size
  • Ionisation
  • Rate of diffusion
19
Q

Explain the movement of ionised molecules across membranes

A

Ionised molecules cannot cross membranes

20
Q

Name the factors effecting absorption from the GIT

A
  • pH
  • Gastric emptying
  • Transporter expression
  • Motility of GIT
  • Interaction of food and drug
21
Q

What is volume of distribution (Vd)?

A

The volume of fluid required to dissolve the amount of drug in the body to give the same concentration as that in the plasma

22
Q

Name the factors that affect Vd (5)

A
  • Local pH differences
  • Binding to macromolecules
  • Dissolution in lipids
  • Active transport
  • Irreversible binding
23
Q

Name some problems encountered with oral administration

A
  • Stomach Acidity
  • Proteolytic enzymes
  • Poor Absorption
  • No absorption
  • Pre systemic metabolism (broken down in first pass)
24
Q

Describe the route of the first pass (pre-systemic) metabolism

A
  • Drugs absorbed from GI tract enter the mesenteric capillary network
  • Absorbed drug is carried via the portal vein to the liver
  • Undergoes hepatic metabolism
  • Metabolites but not parent drug enters the systemic circulation
25
Q

Why don’t drugs absorbed in the buccal cavity and rectum undergo the first pass metabolism

A

they are absorbed straight into the vena cava

26
Q

Gives examples of drugs that can be given intravenously

A

Tubocurarine - muscle relaxant during surgery
Pyridostigmine - reverses the effects of tubocurarine
Thiopental(thiopentone) - general anaesthetic

27
Q

How does perfusion affect intramuscular absorption

A

Larger the blood flow, faster the absorption.

28
Q

Give examples of drugs that can be given through rectal administration

A

Prochlorperazine - vomiting
Diazepam - epilepsy in children
Aminophyline - asthma
Indomethacin - arthritis, esp. morning stiffness

29
Q

Give examples of drugs that can be given by transdermal administration

A

Trinitrin - sticking plaster or ointment
Hyoscine - sticking plaster - motion sickness
Nicotine - sticking plaster - smoking cessation

30
Q

Give examples of drugs that can be given by inhalation

A

Halothane - gaseous/volatile anaesthetics

Salbutamol - local bronchodilators

31
Q

Name the factors that the rate of passive drug diffusion depends on

A
  • conc gradient across the membrane
  • surface area involved
  • membrane thickness
  • partition coefficient of the drug (measure of lipophilicity)
  • Diffusion coefficient of the drug (product of drug size and shape)
32
Q

What does amphoteric mean

A

A molecule/drug with both basic and acidic groups

33
Q

If the dose of the drug is known what can the Vd indicate

A

Vd can indicate which body compartments it has distributed to.

34
Q

What are drugs often bound to as they’re distributed

A

Plasma proteins, tissue proteins or DNA

35
Q

Why do local pH differences affect Vd

A

Can trap drugs in ionised/un-ionised forms

36
Q

How can dissolution in lipids affect Vd

A

Lipophilic drugs can become concentrated in adipose tissue fat droplets

Pharmocolgy (22 decks)

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