Excipients for IR Tablets Flashcards
What are the different immediate release tablets?
Disintegrating tablets
Chewable tablets
How are tablets produced?
Powder compcation
How are immediate release tablets defined?
75% of drug released before 45mins
BP
What is filler used for?
Increase tablet size
>50mg
What are common fillers?
Starch, lactose + microcrystalline cellulose
What is binder used for?
Adhesive to make tablets stick together
Increases compactability
What if too much binder?
Tablet too hard
= hinder disintegration + dissolution
What are common binders?
Lactose, microcrystalline cellulose + pregelantised starch
What is lubricant used for?
Reduce friction between tablet + die
What is anti-adherent used for?
Prevent powder adhesion to punches
What is glidant used for?
Reduce powder cohesion
Improve powder flowability
Improve mixing + content uniformity
What are common lubricants, anti-adherents + glidants?
Magnesium stearate, talc + colloidal silica
How does boundary lubrication work?
Coat particle surface
= slide past each other easily
(Sit at boundary between interface)
= reduce friction
What is the problem with lubricants?
Hydrophobic = excessive amounts impair wetting + dissolution
What does disintegrant do?
Break up tablet into smaller particles
Why does disintegrant increase specific SA?
Expose internal surfaces
What is superdisintegrant?
High performing
More rapid
What is effervescent disintegrant?
Fizzes in contact with H2O
Why do we coat excipients?
Mask taste
Improve ease of swallowing
Reduce friability
Why is friability bad?
Lose powder content during transport
= correct dose not given
What is colouring added for?
Aid tablet identification
What is flavouring added for?
Enhance taste
When is flavouring added?
For tablets that are chewable + stay in mouth for a long time
Can the same excipient exert different amounts?
YES when used at different amounts
Can things like binder + disintegrant be used in same tablet even though they exert opposite functions?
YES
= they do different things at different times
eg. disintegrant only works when in contact with H2O
Describe disintegration
1st step in tablet dissolution
Accelerated by disintegrants
When is disintegration increased?
Higher dissolution rate
Describe mechanism of swelling for disintegration
H2O uptake = forces tablet apart
Degree of swelling depends on particle size
Why are their cross-links in polymers?
Make sure polymers swell BUT don’t break apart when uptake of H2O
Describe mechanism of wicking for disintegration
Create hydrophilic conduits in tablet
= H2O drawn into tablet
Describe mechanism of strain recovery for disintegration
Particles undergo elastic deformation in tablet formation + interlock
= H2O relaxes particles
= return to spherical shape
Describe mechanism of heat of interaction for disintegration
Heat released when particles interact with H2O
= exothermic
= air trapped in tablet absorbs energy + expands
Describe mechanism of interruption of bonding forces for disintegration
Bonds weaken in aq environment
= dissolution
Describe mechanism of repulsion for disintegration
H2O uptake
= electrostatic repulsion between particles
= same charged particles repel
What is an example of superdisintegrant?
Sodium starch glycolate
= cross-linked starch
Describe how effervescent disintegrant work?
Carbonate + bicarbonate break down to CO2 + H2O in acidic conditions
