L53 - Tablet Coating And Drug Release Flashcards
What is tablet coating?
application of coating material to exterior of a tablet to confer beneficial properties as compared to uncoated
What are the 3 main types of coatings are in use?
- sugar
- film
- tablet
Why do you coat tablets? (5)
- ingredients need protection from environment
- mask taste
- easier to swallow
- identification
- controlled release or enteric
What does sugar coating do? (6)
- prevent entry of water
- subcoating - rounding, + calcium carbonate, talc in sucrose solution
- smoothing
- colouring
- polishing
- printing identification
What is film coating like? (3)
- newly-launched coated products film coated
- involved deposition (spraying) of thin film of polymer
- coating liquid contains polymer with other ingredients in liquid
What is tablet coating like?
solution sprayed onto rotating, mixed tablet bed or fluid bed
What is the tablet like sugar vs film coating? (3)
- rounded with polish / retains contour, not shiny
- weight inc 30-50% / 2-3%
- breaklines not possible vs possible
What is the process like sugar vs film coating? (3)
- multistage / single stage
- 8-12 hrs / 1.5-2 hrs
- simple enteric coating / adaptable for controlled release
What are coating problems? (4)
- picking/chipping
- roughness
- sticking
- film cracking/peeling
What is does enteric coating do?
Protect the tablet core from disintegration in acid environment of stomach
Why use enteric coating? (4)
- prevention of acid attack of drug unstable at low pH
- protect stomach from irritation
- facilitate absorption
- taste masking
What are ideal polymers like? (2)
- insoluble in aq media at low pH
- abrupt, well defined inc in solubility at specific pH when inc
What are enteric polymers for direct film-coating? (2)
- cellulose acetate phthalate - CAP
- polyvinyl acetate phthalate - PVAP
what is enteric coat like?
- sealing coat modified to comprise an enteric polymer acrylic derivative
- sufficient weight required for efficiency, 2-3x simple film coating
what is delayed-release tablet like? (4)
- drug core coated with delayed release memb (dry)
- exposure to pH of SI (6.8) dissolves it
- exposed drug core disintegrates
- drug dissolves and is released
what is cumulative amount of drug released like from oral dosage forms? (3)
- immediate - faster plateau
- delayed - delayed plateau
- extended - more linear til plateau
what are typical enteric coating compositions? (5)
- cellulose acetate phtalate, CAP
- glyceryl triacetate
- isopropyl alcohol
- dichloromethane
- water
what are functional multi-particulate coatings like? (4)
- provides opport for design of new m/r oral formulation
- dose divided into 1000s spherical particles 0.5-2.0 mm
- filled, encapsulated or compressed to tablet
- used for C/R medicines w/ GR or ER properties or site specific drug delivery
what are advantages of multiparticulates? (2)
- more consistent GI transit than single dose
- less likely to suffer from dose dumping
what are disadvantages of multiparticulates? (2)
- control of memb characteristics with film coating is difficult
- they are difficult to retain in upper GI tractw
what are properties of multiparticulates? (5)
- good stability
- good flow properties
- high bulk density
- v low hygroscopicity
- easy to dose
what are extruded/spheronised granulates? (2)
- produced in modified granulating equip
- drug granulates extruded thru // mesh under pressure = particles for spheronisation
what are the different drug release mechs from multiparticulates? (3)
- diffusion
- osmosis
- eroison
what is diffusion of multiparticulates like? (4)
- on contact with GI fluids
- water enter interior by diffusion
- dissolution occurs
- drug diffuses across C/R coat
