Practical 2 revision Flashcards
What is a filler
increases the bulk volume of the powder and size, used in low drug doses
(lactose, dicalcium phosphate)
How many forms of lactose
2
A lactose can be
either monohydrate or anhydrous
B lactose is
anhydrous
lactose can be
crystalline and amorphous (more soluble less stable)
how is crystalline lactose formed
formed by precipitation method and according to the crystallization conditions
what is formed by crystalline lactose
a monohydrate or b lactose
how is lactose a monohydrate formed
by the spray drying technique
amorphous lactose dissolves rapidly to crystalline lactose because
it has better compressibility and good flow properties
what is the disadvantages of amorphous lactose
hygroscopic
physically unstable (high temp and humidity
spray dried lactose
what does it consist of
AND what properties does it have
many spherical particles containing micro crystals of a lactose monohydrate with amorphous lactose
excellent flow properties
the amorphous part is responsible for better compressibility
microcrystalline cellulose (what do they have, what do they act as)
have both crystalline and amorphous regions
depends on the position of cellulose chains in the solid
excellent binding properties and acts as a disintegration agent
Fillers (or diluents): inorganic salts: such as dicalcium phosphate dihydrate
what properties does it have?
good flow properties
low cost
but has poor compression characteristics
disadvantages of inorganic salts as fillers (dicalcium phosphate dihydrate)
hydrophilic, easily wetted by water
it is also slightly alkaline so isn’t compatible with ph sensitive drugs
dicalcium phosphate
HIGHLY COMPRESSIBLE AND PROMOTES RAPID DISSOLUTION
It does not contain water of crystallization and can be used with moisture sensitive actives. Its particles are of a size, shape, and density to maximize flow in high -speed tablet production and to reduce tablet weight variation.
anhydrous a lactose
what is it used for
characteristics
disadvantages
used for direct compression with low moisture content
good stability and not sensitive to temperature changes
poor flow properties and low compressibility
what are lubricants
act by interposing an intermediate layer between the tablet constituents and the die wall
what do lubricants act as
the tooling/material interface so they are incorporated in the final mixing step after all the granulation is complete to avoid overmixing
lubricant efficacy depends on
the surface area of the lubricant
What does larger surface area of the lubricant do (brands of magnesium)
significantly decrease in both ejection forces and tablet hardness
what is a common mistake for lubricants
adding both the disintegrate and lubricant together in one mixing step
better to add the excipients sequentially with a DISINTEGRANT being first
what is the mechanism of lubricant action for fluid lubrication
the layer of fluid is located between the die surface and tablet surface
it separates the moving surfaces of the solids from each other which reduces the friction
boundary lubrication
sliding surfaces are separated by a very thin film of lubricant
solid lubricant in the middle of die surface and tablet surface
undesirable effects of water insoluble lubricants
Increase in the disintegration time
Decrease in the drug dissolution rate
Reduction in tablet hardness
