Pharmaceutics: Excipients for IR Tablets Flashcards
What is an IR tablet?
An immediate release tablet is one in which the majority of the drug is released in a short amount of time.
~70-75% of the drug is released in 45minutes.
What excipients are required in the formation of the IR tablet?
- filler (diluent)
- binder
- lubricant
- anti-adherent
- glidant
what excipients are needed for the organoleptic enhancement of IR tablets?
- coating
- colourant
- flavouring
what excipients are required for the dissolution and adsorption of the IR tablets?
- disintegrant
- matrix former
- dissolution enhancer
- absorption enhancer
What is the role of a filler/diluent?
to bulk up the tablet to a minimum size necessary for handling.
What is the role of a binder?
an adhesive that increases compactibility and mechanical strength of a tablet.
What is the role of a lubricant?
to reduce friction between the tablet and the die during ejection. reduces particle-equipment and particle-particle interactions hence lowering friction.
What is the role of an anti-adherent?
to prevent powder/tablet adhesion to punches.
What is the role of a glidant?
to improve powder flow which improves mixing and content uniformity
What is the role of a disintegrant?
to break up tablets into smaller particles which increase SA hence dissolution rate.
What is the role of a coating?
to mask unwanted taste, improve the ease of swallowing, reduce friability and improve stability.
What is the role of a colourant?
to aid tablet identification
What is the role of flavourings?
to enhance tablet taste but isn’t commonly used in tablets for swallowing.
common excipients that can be found in all IR tablets?
- lactose
- natural starch
- pregelatinised starch
- cellulose
- microcrystalline cellulose
- talc
- magnesium stearate
- colloidal silicon dioxide
what does povidone do?
acts as a binder, disintegrant or a dissolution enhancer
what does gelatin do?
acts as a binder that swells upon hydration as it absorbs water.
what are the two types of gelatin?
type A: acid hydrolysed
type B: alkali hydrolysed
what is the first step in tablet dissolution and drug release?
disintegration
how does disintegration affect the dissolution rate?
by increasing the particle surface area hence increases the dissolution rate.
What is used to increase tablet disintegration?
disintegrants
what are traditional disintegrants?
polymers that swell 2-dimensionally upon hydration
what are superdisintegrants?
cross-linked polymers that swell 3-dimensionall upon hydration
what are examples of superdisintegrants?
- Sodium starch glycolate:cross-linked starch.
- Croscarmellose: cross-linked carboxymethyl cellulose.
- Crospovidone: cross-linked PVP
what are effervescent disintegrants?
they produce gas upon hydration
what do carbonates and bicarbonates break down into under acidic conditions?
carbon dioxide and water
proposed mechanism of tablet disintegration is..?
- swelling
- wicking
- strain recovery
- heat of interaction
- interruption of bonding forces
- repulsion
What happens during swelling?
- water uptake causes swelling and the degree of swelling depends on particle size and degree of cross-link.
- occurs in hydrophilic water-insoluble polymers.
what is wicking?
when water is drawn into the tablet due to the formation of hydrophilic conduits (channel) in the tablet.
what happens during strain recovery?
- particles undergo elastic deformation during tablet formation
- then are interblocked before they can relax.
- water in the tablet matrix causes particles to relax.
- particles then regain their original shape and force other particles away.
what happens during heat of interaction?
- exothermic interactions release heat/energy during interactions with water.
- air that’s trapped in the tablet absorbs the energy and expands.
what happens when bonding forces are interrupted?
bonds are weakened/interrupted due to aqueous environment causing dissolution and bonding with water molecules
what is repulsion?
water uptake causes electrostatic repulsion between particles e.g. when particles are ionised in water.
what are the commonly used lubricants?
- magnesium stearate
- stearic acid
- talc
most lubricants are what? hydrophobic or hydrophilic?
hydrophobic
