Powders, tablets and capsules Flashcards
(46 cards)
What are advantages of powder formulation
Chemically more stable than liquid formulations
Preferred form of administration
May provide faster drug dissolution than tablets or capsules
Easier to swallow for very young and elderly populations
What are disadvantages of powder formulation
Accurate dosing is difficult to achieve
Less convenient to administer and transport
Difficult to mask taste and grittiness
Difficult to minimise drug irritation and drug degradation
Barrier packaging required for drugs that are volatile, deliquescent hygroscopic or readily oxidised
What are reasons for reducing particle size
Usually to micron size
For homogenous mixing
To minimise segregation of powders in a powder mix
* Narrow size distribution
* Prevent demixing
To improve drug dissolution rate and bioavailability
To minimise powder grittiness and enhance product acceptance
To optimise drug delivery to deep lungs
What are reasons for increasing particle size
Granulation
Maintain homogeneity of powder mix and reduce demixing
Improve handling
* Powder flow
* Reduce occupational hazards
* Reduce caking and hardening on storage
Improve compaction into tablets
Improve wettability
* Granules are larger to attract wetting agent, becomes close in proximity of wetting agent
Increase bulk density to reduce packing volume and costs of transport
* Powders stick to everything, granules reduce sticking
What is wet granulation
Mix powder with granulating fluid to form wet mass
Mechanisms of particle bonding
Formation of solid bridges between particles
Attractive van der Waals forces between solid particles
Mechanical interlocking of solid particles
Advantages of spheronisation
Same as other granules but smooth surface
* Spherical shapes allows for better flow
Smooth surface facilitates uniform thin layer coating
* Allows for mixing of incompatible ingredients and manufacture of modified release dosage forms
How are dry granulations made
Roller compaction
Milling of sheets/ flakes/ slugs
What is mixing
What is convective mixing
One part of powder bed moves relative to another part
Creates segregated mixture
Small particles with large particles
What is shear mixing
A layer of powder particles moves relative to another layer
This creates an ideal mixture
What is diffusive mixing
Individual powder particles move relative to each other
This creates a random mixture
* Requires velocity to obtain this mixture
* Introduce void space
How do you minimise demixing
Use narrow particle size range or ensure all particles are below 30microns
Control particle shape
Use particles of similar density
Use granulation or ordered mixing
Reduce vibration when processing post-mixed powders
Use one-stop operational equipment
What are the advantages of different drying processes
What are the disadvantages of
Fluidized bed dryin
Microwave
Spray
Freeze
What are the advantages for tablet formulation
Convenient and accurate dosing
Provision for identification
* Different colours
* Indentation
* Score lines
More stable compared to liquids
Controlled drug release possible
Cost effective industrial manufacture
Versatile design
What are the disadvantages for tablet formulation
Peroral BA may not be as good as liquids
Inappropriate for patients who have difficulty swallowing
Does not provide for flexible dosing compared to liquids for paedriatrics
Wet granulation
Dry granulation
Direct compression
Advantages of direct compression
Simplicity of manufacture
No water and drying processes
Faster disintegration and dissolution
Disadvantages of direct compression
Requires a powder with adequate flow and good compressibility
Relatively large particles required
Challenging for
* Drugs with low dose to achieve content uniformity
o <10mg
* Drugs of high dose to achieve good flow and compressibility
o >50mg
Require diluents of specialised grades
Reasons for coating tablets
Protection
Masking of taste
Improve aesthetics
Aid in identification
Confers added strength
Impart functional properties
What are film coating
Uses polymers as coating agents
* Thin layer of polymer film deposited over tablet cores by atomisation of coating liquid
Controlled release function
Enteric coating
* Protect drug from being released in stomach
