Pharmaceutics-Excipients For Film Coating

Question 1

what is coating?

Answer 1

Process by which an essentially dry outer layer of material is applied to a surface.

Question 2

what are the types of coating?

Answer 2

film coating and sugar coating

Question 3

what are film coatings for?

Answer 3

-they’re the principal means of coating for immediate and modified release drugs

Question 4

what are sugar coatings for?

Answer 4

• they’re the traditional means of coating but film-coating is becoming more common now.
• used to mask taste of drugs and the sugar was soluble

Question 5

what three things does film-coating moderate?

Answer 5

• moisture
• air
• light

Question 6

what determines the drug release profile?

Answer 6

the solubility and permeability of the coating

Question 7

what makes a coating safe?

Answer 7

• if it provides product identification

- if it protects the user from the dust of the toxic drug

Question 8

what does ‘modified drug release’ mean?

Answer 8

-it is when the release of the drug is delayed and/or extended

Question 9

how do coatings improve drug stability?

Answer 9

• Make product more robust for handling (e.g. less friable).
• Protect product against oxygen, moisture and light.
• Separate incompatible materials.

Question 10

how does coating influence the usability and user acceptability of the drug?

Answer 10

• improves the ease of swallowing the drug (e.g. smooth, slippery surface)
• improves the organoleptic properties of the drug (e.g. appearance and taste)

Question 11

what are the three types of drug release and what do they mean?

Answer 11

• Immediate release - rapid drug release
• Delayed release - gastro-resistant or enteric. Coating protects drug from gastric degradation and targets drug release in the intestines
• Extended release - coating promotes sustained release or controlled release of drug (i.e. larger dose of drug released over a prolonged period of time). This is not dependent on pH

Question 12

If the coating is insoluble in water, what is used?

Answer 12

an organic solvent is used as the coating solution.

Question 13

why do coatings have low permeability?

Answer 13

• to minimise degradation of core by oxidation, hydrolysis and photolysis.
• Low water permeability for taste masking.

Question 14

Describe the viscosity of coatings?

Answer 14

• low viscosity for good fluid flow through equipment

- increased viscosity when dissolved or dispersed

Question 15

what is the typical thickness of film-coatings?

Answer 15

20-100micrometers

Question 16

why must the film coating had a high tensile strength?

Answer 16

to resist breakage

Question 17

why should the coating be flexible?

Answer 17

so it can deform and not crack in response to stress

Question 18

why do coatings include adhesive?

Answer 18

so they can stick and stay on the core material

Question 19

what are the essential film-coating excipients?

Answer 19

1. polymer
2. plasticiser
3. Solvent
4. Colourant

Question 20

what are the optional excipients for film-coatings?

Answer 20

1. wetting agent

2. anti-tack

Question 21

what is the role of the polymer in the coating?

Answer 21

-the drug is released when the polymer dissolves and/or becomes permeable to water. This is controlled by the substituent groups.

Question 22

for immediate release drugs, what should the substituents on the polymer be?

Answer 22

soluble (hydrophilic) or basic to ionise in the stomach

Question 23

for delayed release drugs, what should the substituents on the polymer be?

Answer 23

non-ionied in the stomach but rapidly ionised in intestines

Question 24

for extended release drugs, what should the substituents on the polymer be?

Answer 24

non-polar for reduced solubility and permeability for slower drug release.

Question 25

what are semi-synthetic polymers?

Answer 25

• they are polymers derived from cellulose coming from a natural source.
• the cellulose substitutes with the side chains of the polymer

Question 26

what are synthetic polymers?

Answer 26

they are designed and assembled artificially

Question 27

what are cellulosics?

Answer 27

cellulose derivatives for immediate, delayed and extended release

Question 28

what are the characteristics of Cellulose derivatives for immediate release?

Answer 28

• Low molecular weight variants.
• Low degree of hydrophobic methyl (CH3) substitution.
• Abundance of hydrophilic hydroxyl (OH) groups.
• e.g. Methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxylpropyl methyl cellulose (hypromellose).

Question 29

what are the characteristics of Cellulose derivatives for delayed release?

Answer 29

Phthalate esters of -cellulose derivatives with phthalic acid.

• contain carboxyl groups which Ionise at 5:5.
• e.g. Hydroxypropyl methyl cellulose phthalate, Cellulose acetate phthalate

Question 30

what are the characteristics of Cellulose derivatives for extended release?

Answer 30

• High molecular weight variants.
• Abundance of hydrophobic alkyl substituents.
• Extensive cross-linking.
• e.g. Ethyl cellulose, cellulose acetate.

Question 31

what are polymethacrylates?

Answer 31

-they are Methacrylate co-polymers, whose properties depend on the chemistry and ratio of different monomers

Question 32

what dictates the release profile of polymethacrylates?

Answer 32

Water solubility and lm permeability

Question 33

For immediate release, what is the solubility of Polymethacrylates?

Answer 33

water soluble in stomach at low pH (acidic conditions)

Question 34

For delayed release, what is the solubility of Polymethacrylates?

Answer 34

water soluble in intestines at high pH (alkaline conditions)

Question 35

For extended release, what is the solubility of Polymethacrylates?

Answer 35

insoluble in water, instead swells to become permeable to let water through to dissolve the drug

Question 36

For immediate release, what is the R group attached to the polymethacrylate?

Answer 36

Amino alkyl

Question 37

For delayed release, what is the R group attached to the polymethacrylate?

Answer 37

Carboxyl

Question 38

For extended release, what is the R group attached to the polymethacrylate?

Answer 38

Ester or Ammonioalkyl

Question 39

what causes swelling in the polymethacryllates for delayed release?

Answer 39

Ionised groups promote swelling by electrostatic repulsion

Question 40

what are vinyl derivatives useful for?

Answer 40

immediate release

Question 41

What is the purpose of plasticisers?

Answer 41

To increase flexibility and reduce brittleness

Question 42

What is the role of bridging molecules?

Answer 42

To mediate intermolecular attraction between polymer chains to allow flexible movement of polymer molecules

Question 43

Which of the two are water soluble and water insoluble dyes and pigments?

Answer 43

Dye-water soluble

Pigment-water insoluble

Question 44

What is the purpose of colourants?

Answer 44

• enhance visual appearance

- aid product identification

Question 45

Why are pigments preferred over dyes?

Answer 45

1. Pigments aren’t absorbed
2. They’re more photostable
3. Have a high opacity
4. Possible to optimise coating permeability
5. Not susceptible to mottling due to solute migration

Question 46

Why are setting agents added?

Answer 46

1. Reduces surface tension of coating solution/dispersion

2. Enhances surface coverage by coating solution

Question 47

Why is anti-tack used?

Answer 47

1. Prevents adhesion of coating to each other or to other surfaces hence preventing fusion