Excipients for Immediate-Release Tablets

What are the two Types of oral tablets?

• Immediate release

• Modified release

What are the types of immediate release oral tablets?

• Disintegrating tablets

• Chewable tablets

What are the types of modified release oral tablets?

• Extended/prolonged release tablets

• Delayed release/gastro-resistant tablets

What defines an immediate-release tablet in terms of drug release?

• Majority of the drug is released in a short time, typically 70% or Q = 75% in 45 minutes as per BP dissolution test.

Are immediate-release tablets usually coated or uncoated?

• They can be either uncoated or coated.

What materials are typically used for coating immediate-release tablets?

• Coatings are typically made of sucrose

• or hydrophilic polymeric films.

What are some excipients used as process aids in tablet manufacturing?

• Lubricants,

• anti-adherents,

• and glidants.

Which excipients aid in tablet formation?

• Fillers/diluents

• and binders.

What excipients enhance the organoleptic properties of tablets?

• Coating polymers/sugar,

• colourants,

• flavourings.

Organoleptic properties refer to the sensory attributes of a product mainly taste, smell, color, texture, and appearance.

organoleptic properties are important because they affect patient acceptability and compliance.

Which excipients are involved in drug release and absorption?

• Disintegrants,

• dissolution enhancers,

• absorption enhancers.

What is the primary function of a filler (diluent) in tablet formulation?

• Bulk up the tablet to a minimum size

• Usually >50 mg necessary for handling

• Important for low-dose drugs

Name 3 common fillers (diluents) used in tablet formulation.?

• Starch

• Lactose

• Microcrystalline cellulose

What is the role of a binder in tablet formulation?

• Acts as an adhesive that makes particles stick

• Increases compactability of powder mixture and tablet hardness

What is a potential downside of using excessive binder?

May hinder tablet disintegration and drug dissolution

Name common binders used in tablet formulations.

• Lactose

• Microcrystalline cellulose

Excipients that prevent particles from sticking

• > lubricant
  > anti-adherent
  > glidant

What is the function of a lubricant

• Reduces friction between tablet and die during tablet ejection

What is the role of an anti-adherent?

Prevents powder/tablet adhesion to punches

What does a glidant do?

• Reduces powder cohesion

• Improves powder flowability

• Enhances mixing and content uniformity

Name 3 common lubricants, anti-adherents, and glidants.?

• Magnesium stearate

• Talc

• Colloidal silica

What causes friction in boundary lubrication, and how do lubricants reduce it?

• Friction between particles and equipment or other particles inhibits particle movement.

• Small, adherent lubricant molecules coat particle surfaces in multiple layers that slide easily past one another.

• Lubricants reduce particle-equipment and particle-particle interactions, lowering friction.

Which excipients commonly function as lubricants in boundary lubrication?

• Magnesium stearate

• Stearic acid

• Talc

What additional roles can lubricants play besides lubrication?

• Often act as anti-adherents and glidants.

Why can excessive amounts of hydrophobic lubricants be problematic?

• They impair wetting and thus reduce dissolution of the tablet.

Excipients that break up a disintegrating tablet?

• > disintegrant
  > super disintegrant
  > effervescent disintegrant

What is the primary function of a disintegrant in tablets?

• Break up the tablet into smaller particles

• Increase specific surface area and dissolution rate

• Follows the principle of the Noyes-Whitney equation

• Usually materials that swell upon hydration

What is a superdisintegrant?

• A high-performance disintegrant

• Promotes more rapid disintegration compared to regular disintegrants

What is an effervescent disintegrant?

• Produces a fizzing reaction on contact with water

• Common in effervescent tablets for rapid disintegration and better taste masking

What is the Noyes-Whitney equation"?

• The Noyes-Whitney equation describes the rate at which a solid dissolves in a liquid. It says that the dissolution rate increases when:

• The surface area of the solid increases

• The concentration gradient (difference between drug at the surface and in the surrounding liquid) is higher

• The diffusion layer is thinner

• The solvent is stirred or agitated

Excipients that enhance organoleptic properties

> coating excipients
> colourant
> flavouring

What are the functions of coating excipients?

• Mask unpleasant taste

• Improve ease of swallowing

• Reduce friability or powdery feel of the tablet

What is the role of colourants in tablets?

• Aid in tablet identification

• Can be dispersed throughout the tablet, in the coating, or used as printing

What is the purpose of flavouring agents in tablets?

• Enhance the taste of the tablet

• Typically used in chewable tablets, not in tablets meant to be swallowed whole

Do all immediate-release (IR) tablets contain the same excipients?

• No, not all IR tablets will contain all of the common excipients

• Some may include other excipients not listed

What makes excipient selection complex in tablet formulation?

• Many excipients are multifunctional

• Some formulations include excipients with opposite effects

• The same excipient can behave differently depending on its concentration

How does excipient selection impact drug release?

• The formulation dictates the release profile

• Different formulations can produce equivalent release profiles (bioequivalence)

What is disintegration?

• first step in tablet dissolution and drug release

•  larger particle surface area means higher dissolution rate

•  it is accelerated by disintegrants

what are the 6 mechanisms of tablet disintegration?

• 1 swelling

• 2 wicking (capillary effect)

• 3 strain recovery

• 4 heat of interaction (wetting)

• 5 interruption of bonding forces

• 6 repulsion

What is the swelling mechanism of tablet disintegration? step 1

• Involves hydrophilic but water-insoluble polymers

• Water uptake causes the polymer to swell, increasing volume

• Swelling creates internal pressure that breaks the tablet apart

• Degree of swelling depends on:
  • Particle size
  • Degree of crosslinking

What is the wicking mechanism of tablet disintegration? step 2?

• Involves the capillary effect

• Creates hydrophilic pathways within the tablet

• Water is drawn rapidly into the tablet through these channels

What is the strain recovery mechanism of tablet disintegration? step 3?

• Particles undergo elastic deformation during compression

• They become interlocked before they can relax (strain)

• Water penetrates the tablet, allowing particles to relax and recover their shape

• This expansion pushes other particles apart, causing disintegration

: What is the heat of interaction mechanism of tablet disintegration? step 4

• Heat energy is released when particles interact with water (exothermic reaction)

• Entrapped air inside the tablet absorbs this energy and expands

• The expanding air pushes particles apart, leading to tablet disintegration

What is the "interruption of bonding forces" mechanism of tablet disintegration? step 5 

• Tablets are held together by interlocking particles and solid bridges

• In the presence of water, these bonds are weakened or interrupted

• Water dissolves bonding agents or forms new bonds with particles

What is the repulsion mechanism of tablet disintegration?

• Water uptake causes electrostatic repulsion between particles due to ionisation of ingredients in water

• Particles of the same charge are pushed apart, leading to disintegration

What are superdisintegrants and how do they work?

• Cross-linked polymers

• Swell extensively upon contact with water

• Promote rapid tablet disintegration

How do effervescent disintegrants work?

• Contain carbonate and bicarbonate salts

• Under acidic conditions, these break down into CO₂ and water

• Carbonate and bicarbonate must first dissociate in water before reacting

• The released CO₂ causes fizzing, helping tablet disintegration

Identify the tablet type from excipients