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PHARM 125 - Pharmaceutics > Coating of Solid Dosage forms > Flashcards

Coating of Solid Dosage forms Flashcards

1
Q

What are some reasons to coat tablets?

A
  • mask taste (original purpose)
  • help with swallowing
  • controlled or modified release
  • improve mechanical strength and flow
  • protection from crumbling in high porosity
  • reduce irritation of the GI tract or protect drug from from acidic environment
  • colours for identification and improved appearance
  • reduce interaction between components
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2
Q

What are the types of tablet coating?

A
  1. Sugar coating
  2. Film coating
  3. Press (compression) coating
  4. Other → enrobing, gel dipping, hot-melt coating
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3
Q

What is the equipment used for sugar coating tablets?

A

Rotating sugar-coating pan with supply of drying air and extraction system to remove dust and moisture

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4
Q

What is sugar coating?

A

Deposition of aqueous sucrose solution (or sugar alcohols like sorbitol → “sugar free”)

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5
Q

What are the steps in sugar coating?

A
  1. Sealing
  2. Subcoating
  3. Coating
  4. Colouring
  5. Smoothing
  6. Polishing
  7. Printing
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6
Q

What happens in the sealing step of sugar coating?

A

Application of polymer coating to tablet core to protect it from moisture, light and oxidation; typically alcohol solutions of 10-30% of specialized resins or polymers are used

Shellac → mixture of aliphatic and alicyclic hydroxy acids and polyesters

Cellulose acetate phthalate (CAP) and polyvinyl acetate phthalate (PVAP) are most commonly used

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7
Q

Why is shellac no longer used in the sealing step of sugar coating?

A

Can compromise bioavailability due to natural polymerization

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8
Q

What happens in the subcoating/coating step of sugar coating?

A

Subcoating → enhances mechanical strength of tablet; subcoating syrup solution is added in small quantities and alternated by subcoating powder in 3-8 layers

Coating → gives 30-50% weight increase of the tablet, rounds off edges of tablet; coating syrup applied stepwise alternated with coating powder for up to 40 layers

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9
Q

What is an example of subcoating syrup?

A
  • gelatin
  • acacia gum
  • sucrose
  • tween 80
  • water qs
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10
Q

Example of subcoating powder formulation

A
  • calcium carbonate
  • colloidal slilica
  • talc
  • sucrose
  • acacia gum
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11
Q

Example of coating syrup

A
  • sodium CMC
  • Colloidal silica
  • titanium dioxide
  • sucrose
  • starch
  • water qs
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12
Q

What is involved in the colouring step of sugar coating?

A

Multiple applications of syrup solutions with colouring materials; usually with the last coating layer

→ colourants include water-soluble dyes, water-insoluble pigments (titanium dioxide, iron oxide)

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13
Q

Are pigments or dyes preferred in the colouring step of sugar coating?

A

Pigments because they are less prone to move to the surface and cause mottling

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14
Q

What is involved in the smoothing step of sugar coating?

A

Smoothing → application of a simple syrup solution; may contain titanium dioxide (1-5%) as opacifier

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15
Q

What is involved in the polishing step of sugar coating?

A

Polishing → gives glossy finish to tablets by application of wax mixtures

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16
Q

Is printing done before or after the polishing step?

A

Doesn’t matter

17
Q

What are some potential problems with sugar coating?

A
  • breakage of tablets during tumbling process
  • non-uniform coating due to poor mixing
  • twinning (tablets sticking together) → from improper drying
  • colour migration during drying when using water-soluble dyes
  • rough tablets may result in marble-like appearance during polishing
  • cracks and fissures from permeation of moisture into the core
18
Q

What is film coating?

A

Involves the deposition of a thin, uniform polymer coating onto the surface of tablets, capsules and multiparticulates

19
Q

What are some advantages of film coating?

A
  • minimal weight increase (5% of tablet core weight)
  • does not change original shape of core
  • reduced processing time; increased efficiency and output
  • allows for modified release
20
Q

What are the three rules for avoiding dose dumping?

A
  1. film coating must be mechanically sound and resist rupture on ingestion of the dosage form
  2. sufficient coating must be applied uniformly across the surface of material to be coated
  3. dosage form must not be chewed or crushed
21
Q

How does the solubility of the coating relate to the release rate?

A

Insoluble → extended release

Water soluble → immediate release

22
Q

What are the three most common polymers used for film coating?

A
  • cellulose derivatives
  • acrylic resin
  • polyvinyl derivatives
23
Q

Why are insoluble pigments preferred colourants for film coating?

A
  • reduce permeability of coating to moisture → improves product stability
  • bulking agent → increases overall solid content in coating dispersion
  • less colour migration
  • opacifying → improved stability of photolabile API
24
Q

Is it possible to have a drug inside the coating?

A

YES

25
Q

What is the most commonly used equipment in coating and how does it work?

A

Side-vented pan/perforated pan coater → adequate mixing and agitation of the tablet bed, sufficient heat input in drying air provides latent heat of vaporization of aqueous solvents

26
Q

What is the difference between airless and air spray coating?

A

Airless → pumped under pressure through small nozzle to achieve atomization; used in large scale coating operations using organic solvents

Air → compressed air is used to atomize coating liquid; used in small scale operations pr aqueous coating formulations

27
Q

How does a continuous film-coating process work?

A

Tablets are rotated down elongated perforated pan and spray nozzle coats the tablets

28
Q

What is fluidized bed coating typically used for?

A

Commonly used to coat for taste masking, enteric and ER coatings of multiparticulates

**also used for drying and granulating

29
Q

What are the three devices used in fluidized bed coating?

A
  1. Wurster process (bottom spray)
  2. Top spray process (granulation or convention mode)
  3. Rotor process (tangential spray) → double chamber
30
Q

What are the advantages, disadvantages and applications of top spray coating?

A

Advantages → large batch sizes, simple setup and easy access nozzle

Disadvantages → limited applications

Applications → aesthetics and enteric coatings (not recommend for SR or tablet coating)

31
Q

What are the advantages, disadvantages and applications of bottom spray/Wurster process?

A

Advantages → moderate batch sizes, uniform and reproducible film characteristics, widest application range

Disadvantages → tedious setup, cannot access nozzles during process, tallest fluid bed machine

Applications → SR, enteric release, layering, aesthetics (not recommended for tablet coating)

32
Q

What are the advantages, disadvantages and applications of tangential spray/rotary mode?

A

Advantages → simple set up, nozzle access during process, high spray rate, shortest machine

Disadvantages → mechanical stress on product

Applications → good for layering, SR, enteric coating (not recommended for friable products/tablets)

33
Q

What are some advantages and disadvantages of press coatings?

A

Advantages → incompatible materials can be formulated together, no solvent needed

Disadvantages → formulation and processing of the coating layer requires some care, problems with lamination

34
Q

What are some potential problems with film coating?

A
  • picking (wet tablets stick and pull film of surface)
  • orange peel (roughness)
  • mottling
  • twinning
  • cracking and edge chipping
  • wrinkling or blistering (film detaches from tablet)
  • tablet logo bridges and infilling logos
35
Q

What are the most important aspects of coated tablets?

A

Appearance and drug availability

36
Q

What are the standards tests for coated tablets?

A
  • content and weight uniformity
  • tablet breaking force
  • friability
  • dissolution test
  • disintegration test
37
Q

What is the difference in time frame for the disintegration test for film versus enteric coating?

A

Film → 30 minutes

Enteric → 1 hour

PHARM 125 - Pharmaceutics (5 decks)

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