Tableting Flashcards
Causes of capping:
air entrapment mechanism of volume reduction compression speed viscoelastic recovery stress and density distribution internal shear stress
Remedies for capping:
lower compression force reduce compression speed decrease ejection path in die tool design change extend dwell time
methods to make tablets:
compression
moulding
printing
Properties of tablets:
contain exact dosage of active principles confer maximum stability possible possess suitable mechanical properties contain only inert additives/excipients aesthetically pleasing suitable for intended purpose
Advantages and disadvantages of tablet as a dosage form
Advantages: - convenient means of administering - delivery of an accurate dose - small and compact - easy to handle and pack - high production throughput possible Disadvantages: - poor compressibility - poor wetting - slow dissolution - high dose - bitter taste/bad odour - sensitivity to moisture
types of excipients:
Major: Diluent/filler binder/adhesive disintegrant lubricant
Minor: absorbant stabiliser wetting agent colorant
properties of diluents/fillers:
inert, inexpensive, good flow, good compactibility
Types of diluents/fillers:
sugars, starches, celluloses, inorganic salts
types of binders/adhesives
celluloses: high strength, low friability, self-lubricant, dry binder
Modified celluloses: dissolved in water and used as liquid binders
synthetic polymers: not absorbed, also used to reduce viscosity of blood, one of the most popular and safe for human consumption
Gums: not as color stable
Types of disintegrants and their mechanisms:
Starch (2-10%): swelling and wicking
MCC (5-10%): wicking, H-bonding
Sodium starch glycolate (1-5% w/w): swelling
Crospovidone (2-5%): wicking, strain recovery
Mechanisms of disintegrants:
Swelling: swelling of the materials to push particles apart
Wicking: Helps matrix become softer and allow other things present inside to swell – commonly used with other types of disintegrants
Strain recovery: compressed when compacted and return to normal state when put in liquid
interruption of particle-particle bonds: water reduces bonds holding tablet together
Heat of interaction:enthalpy change releases heat of interaction that helps to break bonds
Types of lubricants:
Glidants:
Improve flow properties of granules/powders by reducing friction between particles –> ball bearing effect
Lubricants:
reduce friction between granules and die wall during compaction –> forms films on surface
Anti-adherents:
prevent sticking/adhesion of tablet, granules/powders to faces of punches – allow tablet to be separated from die cavity
Forms of lubricants:
Hydrodynamic – fluid type sprayed into mixture
Boundary – can be water insoluble or water soluble
tableting operation of single punch tablet machine
- lower punch in die moves down to create die cavity for granules
- shoe moves over die and fills cavity, scrapes excess granules to level of die table by moving aside
- upper punch descends to compress granules
- upper punch withdraws, lower punch rises to eject tablet
- Shoe shifts tablet to collection chute
- Cycle repeats
Tableting operation of rotatory/multistation tablet machine
- dies on rotating platform (turret)
- each die with upper and lower punches
- Granules from hopper into feed frame covering number of dies
- Lower punch descends, allowing die filling to desired weight+excess
- Lower punch raises to correct level, excess granules removed
- Punches brought to compress granules into tablet
Tabletability
capacity of powdered material to be made into tablet of specific strength under effect of compression pressure
Compressibility
Ability to undergo volume reduction when subjected to applied pressure
compactability
Ability of material to produce tablets with sufficient strength under effect of densification
Attributes of good tablet:
contain correct amount of actives possess good mechanical properties chemically stable correct biopharmaceutical properties choice of excipients essential
Need to ensure correct brittle-plastic balance, flow , moisture content, granule porosity, lubrication
Mechanical strength of tablets affected by:
particle size, distribution, shape Granule porosity moisture content fragmentation and viscoelastic deformation applied load (compaction force) -- usually higher load will lead to stronger tablet time of loading time of unloading elastic stress release upon ejection
Material requirements for tablets:
ideal brittle-plastic balance for good compressibility
adequate granule porosity for compressibility
sufficient moisture content for correct compressibility
good powder flow for ideal tabletability
correct level of lubrication for good compactibility
Segregation challenges in compaction
Achieving good content uniformity:
- substantial risk of segregation at different steps of feeding process from hopper to feeder
- Tendency of feed to segregate increases with large differences in form, size and/or density of particles/granules
Flow must be free and uniform into die to ensure:
- tablet weight uniformity
- tablets with consistent and reproducible properties
