Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Drugs and Disease > Drug Administration and Distribution > Flashcards

Drug Administration and Distribution Flashcards

1
Q

what type of forms can be absorbed across lipid membranes?

A

Non-ionised forms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the ratio of ionised to non-ionised drug dependent on?

A

pH and pKa value of drug

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What does the ratio of ionised to non-ionised drug affect?

A

Whether the drug is absorbed and where is the GI tract it happens

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are examples of molecules that can be absorbed across lipid membranes?

A

Gases (e.g. CO2, O2)
Hydrophobic molecules (e.g. benzene)
Small polar molecules (e.g. H20 and ethanol)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are examples of molecules that cannot be absorbed across lipid membranes?

A 
Large polar molecules (e.g. glucose)
Charged molecules (e.g. Amino acids, H+ ions, Na+ ions)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are drugs?

A

Weak electrolytes i.e. acids of bases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What form do drugs exist in?

A

Equilibrium of charged and uncharged forms

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What is the equilibrium equation for bases?

A

RNH2 + H+ RNH3+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the equilibrium equation for acids?

A

RCOOH RCOO- + H+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is pKa?

A

Dissociation consant (pH at which drug is 50% ionised and 50% unionised, i.e. ratio of 1:1)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is pH?

A 
pKa + log ([RCOO-]/ [RCOOH])
Since log (1/1)= log (1)= 0
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What is the equation when pH and pKa are equal?

A

RCOO- = RCOOH

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens to weak acids when the pH of the environment increases?

A

Ionisation increases

likely to be absorbed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What happens to weak bases when the pH of the environment increases?

A

Ionisation decreases

unlikely to be absorbed

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What changes for each pH unit?

A

10-fold change

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What is the pH of the plasma?

A

7.35-7.45

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

What is the pH of the buccal cavity?

A

6.2-7.2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the pH of the stomach?

A

1.0-3.0

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the pH of the duodenum?

A

4.8-8.2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What is the pH of the jejunum and ileum?

A

7.5-8.0

21
Q

What is the pH of the colon?

A

7.0-7.5

22
Q

What happens in the stomach with a pKa of 4?

A

RCOOH RCOOH
Drug absorption
In the stomach, low pH, push equal towards protanation (uncharged)
In stomach weak acid, largerly protonated, largely uncharged so absorption may occur

23
Q

What happens in the intestine with a pKa of 4?

A

H+ + RCOO-
No drug absorption
As you get into the intestine, pH rises, molecule will split into two, have charged form of drug and very little absorption

24
Q

What happens for basic drugs in the intestine?

A

RNH2 RNH2

Drug absorption

25
Q

What happens for basic drugs in the stomach?

A

H+ + RNH3

No drug absorption

26
Q

What are acidic drugs?

A

E.g. aspirin- mainly non-ionised in stomach- readily absorbed

27
Q

What are basic drugs?

A

E.g. amphetamine- mainly ionised in stomach- poorly absorbed

28
Q

What are neutral drugs?

A

E.g. alcohol, readily abosrbed

29
Q

What are the routes of drug administration?

A

Oral
Sublingual/buccal
Rectal- avoids first class metabolism
Epithelial- topical (skin), corneal, nasal
Inhalation
Injection- intravenous, sub-cutaneous, intramuscular, intrathecal (into CNS epidural ,for speed of onset of action)

30
Q

What are the advantages of the oral route?

A

Administration easy and convenient
No skilled personnel required
Drug preparation need not be sterile

31
Q

What are the disadvantages of the oral route?

A

Effects are slow

Absorption may be incomplete

32
Q

Why can some drugs no be given orally?

A

Ionised throughout pH range of gut (tubocurarine)
Too large to be absorbed (insulin)
Destroyed in the gut by acids, enzymes or bacteria (proteins)
Destroyed in the liver after absorption (GTN)

33
Q

What is the inhalation route useful for?

A

Large surface area of alveoli in lungs

Good pulmonary blood supply

34
Q

What effects can inhalation drugs have?

A

Local effects on the lung (e.g. for asthma, salbutamol)

Systemic effects e.g. GAs

35
Q

What do injected drugs bypass?

A

Difficulties of absorption in the gut

36
Q

What must injected drugs be?

A

Sterile
Drugs can only be given by skilled staff
Exact dose of drug given is known

37
Q

What are the advantages of the intravenous route?

A

Rapid effect
Large volumes can be used
Irritant drug solutions can be used

38
Q

What are the disadvantages of the intravenous route?

A

Rapid delivery to heart, CNS- side effects

Cannot recall drug

39
Q

What are the advantages of the intramuscular and sub-cutaneous routes?

A

Control onset with drug vehicle
Aqueous- rapid effect
Oily- slow effect

40
Q

What are the disadvantages of the of the intramuscular and sub-cutaneous routes?

A

Damage at injection site

Limited to small volumes

41
Q

What does distribution of drugs involve?

A

Drugs getting to the site of action

42
Q

What do drugs need to do?

A

Get out of plasma and into tissues

43
Q

What allows drugs to move easily into interstitial fluid?

A

Capillaries which are leaky (large pores), therefore drugs can move easily around tissues and interact with target cells

44
Q

How do drugs travel around in the bloodstream?

A

Bound to plasma proteins

45
Q

What does bound drug-plasma protein complex mean?

A

Bound fraction retained in plasma
Only unbound fraction can diffuse into tissues
Only unbound fraction is active

46
Q

How are capillaries in the CNS different?

A

No pores

Only lipophillic drugs can cross capillary membrane into CNS ionised drugs excluded

47
Q

What kind of drugs can pass across the placenta?

A

Only lipophilic drugs

48
Q

How will effect of drugs be terminated?

A

Distribution of drugs away from their site of action

Drugs and Disease (25 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions