Brainscape's Knowledge GenomeTM

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


See full index

PharmSci Exam 1 > Lecture 2: Influential Factors in Pharmaceutical Dosage Forms > Flashcards

Lecture 2: Influential Factors in Pharmaceutical Dosage Forms Flashcards

1
Q

What are the three key reasons for dosage forms and drug delivery systems?

A
  1. Optimum drug effectiveness
  2. Maximum drug reliability
  3. Maximum drug safety
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What is the rationale/design for dosage forms and drug delivery systems?

A
  1. disease
  2. drug
  3. disease site
  4. delivery systems
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Why pharmaceutical dosage forms?

A
  1. for safe and convenient delivery of accurate dosing
  2. to protect drug substance from atmospheric oxygen or humidity
  3. to protect drug substance from gastric acid after oral administration
  4. to conceal bitter, salty or offensive taste or odor of a drug substance
  5. to provide liquid preparations of an insoluble or unstable drug in desired vehicle
  6. to provide rate-controlled drug action
  7. to provide site-specific drug delivery
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What are the influential factors in dosage form design?

A
  1. molecular size and volume
  2. drug solubility and pH
  3. partition coefficient
  4. polymorphisms
  5. stability
  6. pKa/dissociation constant
  7. particle size and dissolution rate
  8. membrane permeability
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How can drug diffusion be expressed?

A

Stokes-Einstein equation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the Stokes-Einstein equation

A

D = RT/6pir

D = cm2/sec

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

Relationship between drug diffusion and molecular weight

A

drug diffisivity is inversely proportional to molecular volume

dependent on molecular weight and conformation

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

What are five ways drug solubility and pH can be enhanced?

A
  1. salt formation
  2. ester formation or introduce polar functional group
  3. cosolvent
  4. complex formation
  5. micronization
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Salt formation and drug solubility and pH

A

solubility of an acidic or basic drug is pH dependent

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

Polar functional groups

A 
hydroxy groups
amines
ammoniums
aldehydes
carboxylates
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Cosolvents and drug solubility

A

solubility of phenobarbital in a mixture of water, alcohol and glycerol is significantly higher compared to any of these single solvents

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

Complex formation and drug solubility

A

can be increased by addition of a third substance which forms an intermolcular complex with drug

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

What does micronization do?

A

reduce drug’s particle size

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

What is pH one of the most important factors in the formulation process?

A

it affects solubility and stability

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

B-cyclodextrin

A

enhanced solubility

inclusion complex with indomethacin sodium

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

Partitioning

A

When two immiscible liquids contain a weak acid or base drug, a part of the drug goes to the nonpolar phase and the remaining part of the drug goes to the aqueous layer

Like dissolves like

nonpolar species migrates (partitioins) to the nonpolar layer and polar species migrate to the polar aqueous layer

17
Q

Partition coefficient (P)

A

measure of the drug’s distribution in a lipophilic-hydrophilic phase system and indicates its ability to penetrate biologic multiphase systems

18
Q

Octanol-water partition coefficient

A

commonly used in formulation development

P = (Drug conc. in octanol) / (drug conc. drug in water(

19
Q

Ionizable drug octanol-water partition coefficient

A

P (drug conce in octanol or nonpolar phase) / (1-a) (drug conc. in water or polar phase)

a = degree of ionization

log P = measure of lipophilicity

20
Q

What can the partition coefficient be used in?

A
  1. drug extraction from plants or biologic fluids
  2. Transport/permeation of drugs
  3. Drug absorption from dosage forms
  4. Antibiotics recovery from fermentation broth
21
Q

Polymorphism

A

barbiturates
steroids
sulphonamides exhibits polymorphisms

22
Q

Crystalline

A

poorly soluble

23
Q

Amorphous

A

more soluble

24
Q

Ritonavir or Norvir

A

protease inhibitor

25
Q

What does the physical forms of drugs affect?

A

dissolution rate and its extent of its absorption

26
Q

What does changes in crystal characteristics influence?

A

bioavailability and stability

important implications in dosage form

27
Q

What are pKa and dissociation and constants dependent on?

A
  • pH of medium containing drug
  • affects drug’s absorption, biodistribution and elimination
  • adjust vehicle pH to obtain optimum drug’s solubility and stability
28
Q

Weak acid equation

A

HA = H+ + A-

Ka = K1/K2 = [H+][A-]/[HA]

29
Q

pKa equation weak acid

A

pKa = pH + log [HA]/[A-]

30
Q

pKa equation weak base

A

pKa = pH + log [BH+]/[B] = henderson-hasselbach

31
Q

pH-partition theory

A

drugs are absorbed by passive diffusion depending on the fraction of un-ionized form of the drug at the biological membrane

32
Q

pH-partition theory degree of ionization

A

depends on both their pKa and the solution pH

Ionized drugs are more hydrophilic and have minimal membrane transport compared to unionized form of the drug

33
Q

Solution pH of pH partition theory

A

will affect overall partition coefficient of an ionizable substance

34
Q

pKa and pH relationship

A

pKa of the molecule is the pH at which there is a 50:50 mixture of conjugate acid-base forms

35
Q

HH equation for weakly acidic drugs

A

log ionized conc. (salt) / un-ionized conc (acid)

36
Q

HH equation for weakly basic drugs

A

log un-ionized conc (base) / ionized conc. (salt)

37
Q

Limitations of the pH-partition theory

A
  • does not hold true for most weak acids

- quaternary ammonium compounds are ionized at all pHs but are readily absorbed from GI tract

38
Q

What does the pH-partition theory not take account for?

A
  • large epithelial SA of small intestine compensates for ionization effects
  • long residence time in small intestine compensates for ionization effects
  • charged drugs may interact with opposite charged organic ions, resulting in neutral species which are absorbable
  • some drugs are absorbed via active pathways
  • drug absorption is affected by its lipid solubility
39
Q

Why does aspirin often cause gastric bleeding?

A
  • most of the administered aspirin remains un-ionized in the stomach, it is rapidly taken up by the stomach

PharmSci Exam 1 (4 decks)

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