Pharmaceutics Flashcards
What are the critical excipients in normal aspirin?
- Starch
- lactose
- talc
What are the critical excipients in dispersible aspirin?
- Starch
- Lactose
- citric acid
- calcium carbonate
- Talc
- SLS
What are the critical excipients in enteric coated aspirin?
- Methacrylic acid-ethyl acrylate copolymer (1:1)
- Microcrystalline cellulose
- Lactose..
What are granules?
Aggregates of solid particles that are robust enough to withstand handling
What are granulations?
The process of producing granules
How does wet granulation occur?
- Use a shear or fluidised bed granulator
- Process: mix powder ingredients, then aggregate powder using a suitable binder (solution binder), then dry granules and sieve to select particle size
Stages of granule formulation by wet granulation
1- wetting and nucleation
2- consolidation and coalescence
3- attrition and breakage
What is intragranular bonding)
Bonding of particles working a molecule and it is described by the Rumpf classification.
What are the 5 mechanisms of bonding between granules described in the Rumpf classification?
- Attractive forces between particles
- Attractive forces between immobile films
- Liquid bridges
- Solid bridges
- Mechanical interlocking
What are the attractive forces in the Rumpf classification?
- Distant forces
- Attractive forces between particles: van der waals (all particles) and electrostatic interactions (charged particles)
- Attractive forces between immobile films: absorbed moisture in particle surface
What are the liquid bridges in Rumpf classification?
Capillary forces due to liquid around particles (wet granulation)
What are solid bridges in Rumpf classification?
- Sintering of solid binder (dry granulation)
- Re-crystallisation of liquid binder (wet granulation)
What is mechanical interlocking in Rumpf classification?
- Shape-related bonding
- Rough, angular particles are susceptible to mechanical interlocking
What are pellets?
- Dense, spherical particles (5um-1.5mm)
- Produced from granules by extrusion-spheromisation: agglomeration, extrusion, pelletisation and spheromisation
Similarities between pellets and granules
- Can contain multiple drugs and excipients
- Can be coated individually for modified release
- commonly filled into capsules or pressed into tablets
- Possible to manufacture incompatible ingredients and incorporate into a single dosage form
- Smaller than tablets and capsules - pass through the stomach quicker
- Do not need disintegration
- Better able to pass through pylorus intract
What are the advantages of pellets compared to granules?
- Greater density
- Better flow properties
- Lower friability
- Narrower particle size and distribution
- More uniform packaging
- Smoother surface for more uniform coating
How does extrusion work?
- Use and extruder to compress the semi solid material through a screen
- Produces elongated, rodshaped extrudate of uniform diameter
- Screen size and shape dictate extrudate size and shape
What are the extrusion parameters?
- Starting material properties
- Extruder design
- Extruder speed
- Extruder temperature
How does spheronisation work?
- Use a spheroniser - particles are placed on a rotating friction plate, broken into smaller particles and rounded through collision with friction plate (has patterns eg crosshatching), spheroniser wall or each other
- Produces spherical pellets
Mechanism of spheronisation
- Plastic deformation
- Dumb-bell break-up
- Attrition - agglomeration
Spheronisation parameters to control:
- Friction plate rotational speed
- Charge volume/ mass
- Retention time
What are the critical excipients for children?
- Ethanol
- Propylene glycol
- Parabens
- Benzyl alcohol/ benzoates
- Sugars/ sweeteners
Can you give licensed phenobarbital to children?
No - NHS never event
Contains 38% alcohol
- tablets can be crushed and dispersed or use alcohol free liquid if possible
What are the principles of effective drying?
Effective heat and mass transfer
