Tablets 2 Flashcards
Granules need to be ___ into tablets of correct weight, hardness and size
compressed
The tablets need to be ___ enough to withstand handling and shipping but must ___ and/or dissolve in a specific time
hard
disintegrate
What are the two kinds of available tablet presses?
- single punch or multi-station rotary press
What is the process of compression?
process of pressing material to make it more firm and solid
The force pattern is complex, but may be considered an ___ force causing compression and a ___ force exerted by the die wall
axial
radial
___ force between granule mass and die wall resists consolidation
Frictional
What are the two main events of tableting? Describe them
- compression (reduction in bulk volume by elimination of air)
- increase in mechanical strength of mass due to particle/particle interactions (consolidation)
- bonds form during consolidation and on decompression some break due to elastic properties of the mass
- if sufficient bonds remain tablet formed
What are almost all tableting problems a result of?
poor granulation
Describe the “binding and sticking” tableting problem
- tablets ejected with difficulty often accompanied by a grunting sound
- inadequate or uneven lubrication of the granules
- granules too dry or too wet
- die dirty or scratched
- worn die
Describe the “picking” tableting problem
granules material sticks to the punk faces leaving the tablet with a pitted surface
- inadequate or uneven lubrication of the granules
- granules under dried
- -scratched or damaged punch face
Describe the “capping” tableting problem
on decompression, top of tablet becomes detached
- worn tooling
- compression speed too fast
- excess fines
- punch fits too tightly into die
- excessive pressure
- insufficient or ineffective binder
- over dried granules
- crystal habit of drug may have changed
What is the uniformity USP 905 test?
may be determined by weight variation if:
- tablets are uncoated
- contain more than 50 mg of active drug and
- if the active component provides more than 50% of the total weight
- otherwise content uniformity testing must be done
- weight variation
- for tablets meeting the criteria, weigh 10 tablets and -calculate the contents of active ingredient in each based on assay results
- -(assume homogenous distribution, all tablets must contain 85-115% of the labeled amount and the relative standard deviation must not exceed 6%)
- of one unit is outside of these limits, a further 20 tablets are weighed
- requirements for test are met if no more than 1 unit out of the 30 is outside the 85-115% range and the RSD of the thirty tested does not exceed 7.8%
- if tablets do not meet criteria, content uniformity done by assay of 10 units individually and proceed as above
What is the disintegration USP <701> ?
- time required for tablet to disintegrate in a specified test fluid at a specified temperature
- limitations in extrapolating to bioavailability so dissolution testing usually required
- USP test consists of an apparatus into which 6 tablets are placed each into a cylindrical tube which is covered at the bottom by a 0.025 square inch wire screen
- tubes are raised and lowered through a distance of 5.3 to 5.7 cm 29-32x per minute
- plastic disks may or may not be required
- disintegration complete when no solid material with a palatable core remains on the mesh
- if 1 or 2 tablets fail, a further 12 tablets are tested
- the conditions of the test are met if no more than 2 tablets of the 18 tablets fail
What is the dissolution USP <711>?
- time required for a tablet to dissolve in a specified test fluid at a specified temperature
- some correlation to bioavailability
- apparatus is of 2 types
- types 1 apparatus consists of a 1000 mL glass vessel, a motor with a shaft and a cylindrical basket made of a metal screen (40 mesh)
- mesh must be stainless steel or gold plated
- type 2 apparatus same except that a paddle is used in place of the basket
- glass vessel is filled with the fluid and held at the specified temperature
- a tablet placed into each of the baskets or into the vessel if the paddle is used
- rotation speed is specified in the monograph and the time required for dissolution is specified in the monograph
- the quantity of drug which must be in solution (Q) within that time period is also specified in the monograph
What is the friability USP <1216>
- used to assess how tablet will withstand handling and general wear and tear
- uses an apparatus with a revolving drum which drops the tablet a specified distance a specified number of times
- tablets (5-20) are weight, places in the apparatus, tested and then reweighed
- weight loss of more than 0.8% is usually the limit
- test is now in the process of becoming an official test
What is the hardness test?
- unofficial
- a compression force when applied diametrically to a tablet just fractures it
- unites may be kg or kN
- usually tablet on an anvil and the force is transmitted to it by means of a moving plunger
- tablet hardness assessed to determine ability of tablet to withstand shocks during handling and shipping
- also correlates with disintegration and dissolution
What is hardness a function of?
- compression force during pressing, particle density and size, tablet shape and components of the formulation
- established in house and frequently used as an in process assessment of disintegration
- usual minimum hardness for an uncoated tablet is 5 kg
What are the 3 categories of tablet coating?
- sugar coating, film coating and compression coating
What are the basic processes used for applying coating (2)?
- pan coating and air suspension coating
Wha is the purpose of coating tablets?
- used to mask unpleasant doors and tastes
- to protect an ingredient from decomposition
- to improve product elegance
- can be used to control release rate
Describe sugar coating?
- process may take several days - some partly automated systems are faster
- must have good control of humidity, temperature and dust
- variety of coating pans used and each must be equipped with hot and cold air inputs
- tablets core must be an optimal convexity and be quite hard (have to withstand abrasive effect of coating)
- finished tablet must still have the appropriate disintegration/dissolution properties and USP monographs provide these specific details for testing
What are the different processes involved in sugar coating?
- sealing
- subcoating
- syruping
- finishing
- polishing
Tablet cores usually represent ___ by weight of the finished tablet
50%
Describe film coating
- accomplished by decomposition of one or more film forming polymers on the surface of the tablet
- usually film represents less than 5% of the finished tablet weight
- coating can be enteric or non-enteric
What are the qualities that film forming material should have?
- soluble in solvent suitable for processes
- soluble in GI fluids
- form a strong continuous film which is smooth and elegant
- stable to heat, light, air, moist and drug in the product
- have no appreciable taste, odor or color
- able to support pigment or coating additives
- non toxic
- crack resistant (usually by inclusion of additive)
What is the differences in coating between an enteric vs a non-enteric coating?
- non- enteric materials- cellulose derivatives
- enteric materials- phthalate esters of cellulose
What is used to prevent the film from chipping?
- a plasticizer
What are common solvents used in coating?
- alcohols, esters, chlorinated hydrocarbons, acetone, and other ketones
What kind of coating can be used to prevent damage to the environment?
- aqueous based
Describe compression coating
- core placed in centre of a larger die and surrounded with coating material in the form of free flowing granules which is compressed into a final product
- incompatible drugs may be formulated this way
- may also be used for repeat action tablets where the first dose in the coating and a second dose in much slower disintegrating core
- layered or laminated tablets are also common for these purposes
