L29 - Recap Of Bioavailability, Dissolution And Membrane Transport Flashcards

1
Q

What is pharmacodynamics?

A

What the drug does to the body

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

What is pharmacokinetics?

A

what the body does to the drug

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

What is bioavailability?

A

A quantitative measure of the amount of a drug that reaches its site of action and of the rate at which it gets there

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

What does LADME stand for?

A

Liberation
Absroption
Distribution
Metabolism
Excretion

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

What two steps does drug appearance in blood demand?

A
  • release - drug dissolves at administration site
  • absroption - drug crosses biomembrane to reach blood
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is typical of hydrophilic molecules?

A

Drugs is rapidly released, membrane transport is slow

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

What is typical of lipophilic molecules?

A

A poorly soluble drug, easily permeates the biological membrane

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

What two steps are involved in the dissolution of a solid crystal in a liquid?

A
  • solvation - create a stagnat layer of saturated solution
  • diffusion - dissolved molecules move across layer into bulk solution
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the solubility of weakly acidic/basic drug can be predicted by?

A
  • pH of the solution
  • pKa
  • solubility of free (unionised) form of drug
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What is the equation of weak acids as a function of pH?

A

Log Cs-S0/S0 = pH - pKa

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

What is the equation of weak bases as a function of pH?

A

Log S0/Cs-S0 = pH - pKa

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What are the different types of membrane transport?

A
  • transcellular pathway
  • paracellular pathway
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What is passive diffusion?

A

(Main pathway of drug absorption)
- solutes diffuse into cells down a conc grad, partition into the lipid bilayer and out again into cytoplasm

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

What are the different types of transcellular absorption?

A
  • passive diffusion
  • aqueous pore
  • facilitated diffusion
  • active transport
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What is the aqueous pore pathway?

A

Hydrophiic channel created by transmembrane aquaporin protein
- allow transport of small neutral solutes such as urea and glycerol

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

What is facilitated diffusion?

A

Carrier nediated transport of a drug down a conc grad

17
Q

What is active transport?

A

Carrier mediated transport of a drug down or against a conc grad
- requires energy input

18
Q

When does flux occur?

A

A system not in eq moves towards eq
- flow/flux must occur

19
Q

What factors affect flux?

A
  • conc
  • velocity
  • area
20
Q

When does flux increase?

A

with membrane SA (A)

21
Q

What is flux inversely proportional to?

A

Membrane thickness (deltax)

22
Q

What is flux directly correlated to?

A

difference between drugs conc on either side of membrane

23
Q

What are membrane properties, drug properties and drug & membrane properties in fick’s first law of diffusion?

A

Membrane - membrane thickness, area

Drug - conc grad, parition coefficient

Drug & membrane - diffusivity

24
Q

What is the partition coefficient?

A

K
Quantifies distribution of drug between membrane and aqueous phases which it separates

25
What does a drug’s lipophilicity affect?
- absorption - distribution - elimination
26
What must a drug be like in terms of lipophilicity?
Lipophilic to cross cell membranes - not too lipophilic as may be deposited in fatty tissue
27
What is the pH parition hypothesis?
Drug accumulates on the sideof the membrane where pH favours ionisation
28
What is membrane transport like when AH and B (unionised drug) is lipophilic?
Optinal membrane transport
29
What is membrane transport like when A- and BH+ (ionised drug) is hydrophilic?
Reduced membrane transport
30
What are the limitations of the pH partition hypothesis? (7)
Doesn’t take into account - type of epithelicum - SA of absorption site - ionised drug absorbed to a small extent - active transport of drugs - residence time of drug at delivery site - mass transfer of fluids - charged drug pairs
31
Why and what is lipinki’s Ro5 used for?
- considers physiochemical properties of a drug candidate in terms of potential bioavailability - predicts good oral bioavailability
32
What is the criteria for a good oral bioavailability with Ro5?
- MW < 500 - logP < 5 - H bond donors < 5 - H bond acceptors < 10 - all units are multiples of 5