Coated Tablets Flashcards
What is coating (the process)?
Process that applies a dry outer layer of material to the surface
What coating (layer)?
Outer layer of material itself
What are the different types of polymer film coatings?
Immediate release (non-functional)
Modified release (functional)
What is immediate release referred as?
Film coating
What did immediate release replace?
Sugar coating
Why does immediate release not modify drug release rate?
Dissolves rapidly
Which coatings fall under modified release?
Enteric
Release
Gastro-resistant
Extended release
What is the primary role of modified release?
To control drug release rate
What are the reasons for tablet coating?
Improve tablet friability
Protect against oxygen, moisture and light
Improve ease of swallowing
Modify drug release profile
Describe immediate release of a drug
Rapid drug release
>75% in 45min
Describe delayed release of a drug
Gastro-resistant
Protects drug from gastric degradation
Drug release into intestines
Describe extended release of a drug
Sustained release or controlled release
Releases a larger dose over a prolonged time period
How do you know when it’s sustained release?
On the graph
Decreases to zero or down
How do you know when it’s controlled release?
On the graph
Plateaus
Why use extended release?
Keep in therapeutic range longer
Reduce amount of doses
Increase patient adherence
What is in film coating formulation?
Polymer
Plasticiser
Solvent
Colourant
Wetting agent
Anti-tack
What is semi-synthetic polymer derived from?
Cellulose
What is synthetic polymer derived from?
Designed + assembled artificially from monomers with different side chain chemistry
Describe the formulation for immediate release
Readily dissolve in H2O
= substitute OH for R group
Describe formulation for delayed release
Soluble in alkaline/ neutral = small intestines
= substitute acidic groups = dissolve in alkaline environment
Describe formulation for extended release
Want to dissolve slowly
= add alkyl groups (hydrophobic) + cross links
Describe cellulose derivatives for immediate release
Low molecular weight
Hydrophobic methyl substitution
Abundance of hydrophilic OH groups
Describe cellulose derivatives for delayed release
Phthalate esters of cellulose derivatives
Carboxyl groups
Describe cellulose derivatives for extended release
High molecular weight
May be crosslinked
Abundance of hydrophobic alkyl substituents
Which polymethacrylates are used for immediate release?
Aminoalkyl methacrylate copolymers
Which polymethacrylates are used for delayed release?
Methacrylic acid copolymers
Which polymethacrylates for extended release?
Aminoioalkyl methacrylate copolymers
What are vinyl derivatives used for?
Immediate release
What is the purpose of plasticiser?
Increase film flexibility, reduce brittleness
What are examples of plasticisers?
Polyols - propylene glycol
Esters - diethyl phthalate
Oils - mineral oils
What determines the ability of plasticisers?
Hydrogen bonding ability to bridge polymer chains
What are the 2 types of colourants?
Dye
Pigment
What is a dye?
Water-soluble
What is a pigment?
Water-insoluble
What are the purpose of colourants?
Enhance visual appearance
Aid product identification
Why are pigments preferred over dyes?
Not absorbed
More photostable
High opacity
