oral powders Flashcards
powder as a dosage form meaning
describes a formulation in which a drug powder has been mixed with other powdered excipients to produce the final product
meaning of a powder as a precursor of a dosage tablet
can be a precursor of tablets either
- directly (powder compressed to form a tablet)
- indirectly (via granules)
what do granules mean as a dosage form
granules as dosage forms are powder particles that have been aggregated to form a larger particle 2 to 4 mm diameter
granules as a precursor of a dosage form
granules can also be an intermediate of tablet manufacturing
(typically 0.2-0.5mm)
advantages of powders and granules compared to tablets/capsules/liquids
- more stable than liquid
- convenient for large doses (1-5g)
- faster dissolution rate than capsules or tablets
disadvantages of powders and granules compared to tablets/capsules/liquids
- less convenient to carry than tablets/capsules
- difficult to mask unpleasant taste
- not suitable for administration of potent drugs
- not suitable for drugs inactivated in the stomach or that can cause stomach damage
what powders and granules are used orally
- bulk powders or granules for internal use
- divided powders or granules (single preparation)
non oral administration routes of powders and granules
- dusting powders for external use
- insufflation (ear/nose/throat)
- antibiotic syrups
- powders for reconstitution into injections
- dry powders inhalers
what can particle size affect
- drug bioavailability
- settling rate
- possibility of obtaining homogenous mixtures
- flowability
- tolerability of some dosage forms
what factors favour powder flow
- gravity
- true density of particles
- angle of the surface over which particles are flowing
what factors are against powder flow
- adhesion forces (particles and container)
- cohesion forces (particles-particles)
why do fine powders have higher cohesion
because they have higher surface/mass ratio
can particle shape affect the flow
yes
how does angle of repose work
you put powder into a funnel and pour it out into a cone shape
a low angle of repose allows good powder flow
what does it mean if theta is high (angle of repose)
the powder is cohesive
what does it mean if theta is low (angle of repose)
powder is non cohesive
what is bulk or apparent volume
the volume occupied by a powder including the pores
(ie the empty gaps between particles)
what is the tapped volume
the volume occupied by a powder after tapping
what is the true volume
the volume occupied by a power excluding the volume occupied by the pores
formula for bulk density
mass / Vbulk
formula for true density
mass / Vtrue
is the bulk density of a powder less or more than the true density
less
what is the K true density
the bulk density
formula for bulk density
mass / Vbulk
formula of true density
mass / Vtrue
formula for K
bulk density / true density
or
Vparticles / Vbulk
what is porosity
the (%) voidage of the powder bed
what does high porosity mean
water can get into particles really quickly
what are the 3 porosity formulas
Vpores / Vbulk
or
(Vbulk - Vparticles) / Vbulk
or
1 - (Vparticles / Vbulk)
what is granulation
the process in which homogenous mixtures of primary powder particles from larger particles called granules
3 main advantages of granulation
- improve powder flow
- prevent segregation
- improve compaction (ie tableting)
other reasons for granulation
- reduce generation of dust (good for toxic compounds)
- they retain flowability even after absorbing moisture
- granules occupy less volume (good for storage)
what are the types of granulation
- wet granulation
- dry granulation
wet granulation process
- powders are mixed with a granulating fluid
- the mass is forced through. sieve
when would wet granulation be the usually favoured choice
when the tablets contain larger amounts of the drugs
chemistry behind wet granulation
- adhesion and cohesion forces in immobile films
- interfacial forces in mobile liquid films
- solid bridges (hardening binders or crystallisation of dissolved substances)
- attractive forces between particles
dry granulation process
- a pressure is applied
- the intermediate product is broken
- sieving
chemistry of dry granulation
- attractive forces between solid particles
- solid bridges formed by partial melting
