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Drugs and Disease > Drug Administration > Flashcards

Drug Administration Flashcards

1
Q

Define absorption:

A

The passage of a drug from its site of administration into the plasma

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2
Q

For what administration is absorption not a factor?

A

Intravenous injection

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3
Q

What is the absorption process in oral administration?

A

Little occurs until the small intestine

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4
Q

What is the absorption process in sublingual administration?

A

Absorption in the oral cavity

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5
Q

When would absorption through the oral cavity be useful?

A

If a rapid response is required

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6
Q

When you you use rectal or vaginal administration?

A

To produce a local effect

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7
Q

In epithelial application where is the drug normally applied?

A

The skin, the cornea of the eye or the nasal mucosa

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8
Q

What is administration to the skin otherwise known as?

A

Topical

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9
Q

When would you use inhalation as an administration?

A

For volatile substances

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10
Q

What are the four types of injection?

A
  1. Intravenous injection
  2. Subcutanous/intramuscular
  3. Intrathecal
  4. Epidural
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11
Q

What does it mean when you say drugs are weak electrolytes?

A

They are acids and bases that exist in an equillibrium of charged and uncharged forms

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12
Q

What form of the drug can cross the cell membrane?

A

Only the uncharged ones (hydrophobic) can cross the cell membrane

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13
Q

In acids, is the ionised form protonated or deprotonated?

A

Depronated (AH-)

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14
Q

In bases, is the ionised form protonated or deprotonated?

A

Protonated (BH+)

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15
Q

In acids, is the ionised form protonated or deprotonated?

A

Depronated (A-)

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16
Q

The ratio of uncharged to charge is dependent on what?

A

pH and pKA

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17
Q

How can you work out the ratio of charged to uncharged?

A

Using the Henderson Hasselbach Equation

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18
Q

What is the PKA

A

The dissociation constant: how easily it can pick up or lose an electron

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19
Q

If an acid has a ph thats one unit higher than the pka what will the ionisation be?

A

10:1 of ionised:unionised

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20
Q

If an acid has a ph thats two units higher than the pka what will the ionisation be?

A

100:1 of ionised:unionised

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21
Q

What are three advantages of oral administration?

A
  1. Easy and convenient administration
  2. No skilled personnel required
  3. No need for steralisation
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22
Q

If the stomach pH is 2 how well absorbed would an acidic drug be and how would you work this out?

A

An acidic drug would have a pKa of about 5 meaning if you take the inverse log you get a ratio of 1:1000 ionised:deionised meaning that the drugs are readily absorbed

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23
Q

If the stomach pH is 2 how well absorbed would a basic drugs be and how would you work this out?

A

Basic drugs have a ph of higher than 7 and therefore if you take the inverse log you would get a ratio of about 1:100000 deionised to ionised therefore these drugs would not be readily absorbed

24
Q

If the stomach ph is 2 how well absorbed would neutral drugs be? What is an example of a neutral drug?

A

Readily absorbed and alcohol

25
Q

What is an example of an acidic drug?

A

Aspirin

26
Q

What is an example of a basic drug?

A

Amphetamine

27
Q

If the duodenum has a ph of 8 will acidic drugs be readily absorbed? How do you work this out?

A

Since the pka of acidic drugs is about 5 the ratio of ionised to non-ionised is about 100:1 so is not readily absorbed

28
Q

If the duodenum has a ph of 8 will basic drugs be readily absorbed? How do you work this out?

A

Basic drugs have a Ph normally above 8 so therefore will be have a higher ionised:deionised ratio and will be readily absorbed

29
Q

Theoretically the duodenum should not absorbed acidic drugs, why is this?

A

It has an incredibly large surface area - major site of absorption for basic, acidic and lipophillic drugs

30
Q

What are the disadvantages of using the oral route of administration?

A

Not fast acting and absorption may be incomplete

31
Q

Tubocurraine cannot be given orally; why is this?

A

Is ionised throughout the ph range of the gut

32
Q

Insulin cannot be given orally; why is this?

A

It is too large to be absorbed

33
Q

What are some reasons why drugs cant be given orally?

A

They are destroyed by first pass effect in the liver after they are absorbed or are destroyed by enzymes, bacteria and acid in the gut

34
Q

What kind of affects can inhaled drugs have?

A

Local or systemic

35
Q

What is an example of a drug that is inhaled and gives a local effect? What could it be used to treat?

A

Salabutamol has an effect on the lung when inhaled used to treat asthma

36
Q

What is an example of a drug that is inhaled and gives a systemic effect? What is it used for?

A

halothane is a general anesthetic

37
Q

What is an advantage of using an injection as a route of administration?

A

They are not absorbed so by pass any difficulties associated with it

38
Q

What are some disadvantages of injection that other administration routes don’t have?

A

The drugs have to be sterile and administered by skilled personnel

39
Q

What is a very important factor when administering an injection?

A

The exact dose must be known

40
Q

What is an intravenous injection?

A

Injection into the vein

41
Q

What are three advtantages of intravenous injection?

A
  1. Irritant drugs can be used
  2. Large volumes can be used
  3. Rapid action
42
Q

What is an disadvantage of intravenous injection?

A

You cannot recall the drug

43
Q

What is subcutaneous/intramuscular administration?

A

Injection into the layer between tissue and muscle

44
Q

What are three advantages of the subcutaneous route?

A
  1. Use a drug vehicle
  2. Oily - slow effect
  3. aqueous - rapid effect
45
Q

What are the disadvantages of the subcutaneous route?

A

Can damage the site of injection and can only use small volumes

46
Q

What are 6 important factors when it comes to deciding what kind of administration should be used?

A
  1. The chemical nature of the drug - looking at how it will be absorbed and if it will be irritant
  2. How quickly the effect is required i.e. for a fast effect you wouldnt use oral administration
  3. How long the effect should be maintained
  4. The patients condition
  5. The patients compliance
  6. Convienience - it would not make
47
Q

What are 6 important factors when it comes to deciding what kind of administration should be used?

A
  1. The chemical nature of the drug - looking at how it will be absorbed and if it will be irritant
  2. How quickly the effect is required i.e. for a fast effect you wouldnt use oral administration
  3. How long the effect should be maintained
  4. The patients condition
  5. The patients compliance - not as important as sometimes decisions must be made for them if
  6. Convienience - of least important
48
Q

How do the drugs get out of the plasma and into the tissues?

A

Through leaky pores in blood vessels allows them to get into the interstitial fluid

49
Q

Why is drugs getting into the interstitial fluid important?

A

The interstitial fluid surrounds the tissues so the drugs can therefore interact with the target cells

50
Q

Why might plasma protein binding affect drug distribution?

A

Because only the unbound protein can diffuse into the tissues and is therefore active

51
Q

What is an extreme example of a drug that is highly bound to plasma proteins?

A

Warfarrin

52
Q

What is different about the capillaries in the CNS? What barrier is this better known by?

A

They have no leaky pores. The blood brain barrier

53
Q

What drugs can therefore cross into the CNS and what drugs cant?

A

Only lipophillic drugs can cross the membrane and ionised drugs and excluded

54
Q

What is another example of a good barrier to drugs and what kind of drugs can cross it?

A

The placental barrier - only lipophillic drugs

55
Q

What terminates the effect of drugs?

A

Distrubution of the drugs away from their site of action

56
Q

What is an example of a drugs that would distrubute away from its site of action and therefore terminate its effect?

A

Local anasthetics e.g. lidocaine

57
Q

How would you prevent drugs from distrubuting away from their site of action?

A

Keep them there using a vasnconstrictor such as adrenaline

Drugs and Disease (15 decks)

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