Powders & Tablets Flashcards
Define pharmaceutical powders.
Pharmaceutical powders are mixtures of solid particles that can be APIs or mixtures of APIs and excipients. They can serve as dosage forms themselves or as precursors to other formulations.
List the advantages of tablets as dosage forms.
- Convenient to manufacture and use.
- Easy to take (no special conditions).
- Portable.
- Easy to scale up production.
- Versatile machinery for manufacturing.
- Controllable release rates (e.g., sustained or effervescent tablets).
What are the 4 ways of describing particle size?
- Projected area diameter.
- Projected perimeter diameter.
- Feret’s diameter.
- Martin’s diameter.
Why is particle size important in pharmaceutical powders?
It affects:
• Drug bioavailability (via dissolution).
• Settling rate in suspensions.
• Homogeneity of mixtures.
• Powder flowability (directly proportional to particle size).
• Tolerability of some dosage forms (e.g., inhalers).
Define bulk and true volume.
• Bulk volume: Total volume of the material, including inter-particle voids.
• True volume: Volume occupied by the material itself.
The bulk density is always less than the true density.
What are the main methods of particle size reduction?
- Cutting methods.
- Compression methods (e.g., roller mills).
- Impact methods (e.g., hammer mills).
- Attrition methods.
- Combined impact and attrition methods (e.g., ball mills).
What factors affect the choice of mill used for particle size reduction?
• Desired particle size.
• Material characteristics (elastic, brittle, etc.).
• Cost, time, and ingredient stability.
• Available equipment.
Define excipients and state their purpose.
Excipients are pharmacologically inert materials added to dosage forms to improve their characteristics, manufacturing efficiency, and quality.
Name examples of fillers used in tablets.
• Water-soluble fillers: Lactose, glucose, mannitol.
• Water-insoluble fillers: Cellulose, starch, calcium hydrogen phosphate.
What are disintegrants, and how do they work?
Disintegrants promote tablet breakup into smaller particles upon ingestion to release the API. Examples: Crospovidone and sodium croscarmellose.
What is the function of lubricants in tablet formulation?
Lubricants reduce friction between particles and equipment, improving powder flowability. Examples: Magnesium stearate (max 1%), talc.
What is the main aim of mixing in pharmaceutical formulations?
To obtain a homogeneous distribution of two or more components without physical or chemical changes.
What factors affect mixing and segregation?
- Particle size
- Particle shape
- Density
- Flowability
- Component ratio
- Mixing time
- Electrostatic interactions
- Total powder volume
- Friability
- Humidity
What are positive, negative, and neutral mixtures?
- Positive mixtures: Mix spontaneously and irreversibly.
- Negative mixtures: Tend to separate.
- Neutral mixtures: Neither separate nor mix readily.
What is the relationship between particle size and mixing homogeneity?
Smaller particle size increases the chance of an even distribution but makes it harder to achieve uniformity in low-proportion components.
Name three types of mixers used for powder mixing.
- Tumbling mixers (e.g., Y-cone, V-mixers)
- Agitator mixers
- Rotating cube mixers
What is granulation, and why is it important?
Granulation forms larger, homogeneous granules from primary powder particles.
Importance:
* Improves powder flow.
* Enhances compaction properties.
* Reduces segregation.
* Reduces dust generation.
* Improves storage convenience.
What are the key steps of dry granulation?
- Mix API and excipients.
- Compress into sheets or flakes using rollers.
- Mill sheets to form granules.
- Sieve granules for the required size.
- Add lubricant.
- Compress into tablets.
What are the advantages and disadvantages of wet granulation?
- Advantages:
- Lower cost compared to dry granulation.
- Multi-purpose machines available.
- Disadvantages:
- Requires multiple machines.
- Drying time and temperature can affect drug stability.
- Risk of water/solvent hydrolysis.
Name two pieces of equipment used for both granulation and drying.
- Fluidized-bed granulator
- Spray drier
What is the purpose of drying in tablet manufacturing?
To remove liquid from wet solids, improving granule strength and flowability.
What are the advantages of fluidized-bed drying?
- Short drying times
- Uniform temperature
- Constant rate drying
- Reduced sieving need
What are the three steps of tablet formation?
- Filling: Powder or granules fill the die cavity.
- Compression: Content is compressed into a solid mass.
- Ejection: The compressed tablet is removed from the die.
What are the British Pharmacopoeia (BP) quality control tests for tablets?
- Appearance
- Uniformity of content
- Uniformity of weight
- Disintegration test
- Resistance to crushing (hardness test)
- Friability
- Dissolution
What is the aim of the uniformity of content test?
To ensure individual tablet content varies within acceptable limits (85–115% of average content).
How is the friability of tablets tested?
- Weigh a sample of tablets.
- Rotate in a friabilator.
- Weigh tablets again and calculate % weight loss.
- Acceptance criteria: Loss ≤ 1%.
What is the disintegration test?
It measures the time for tablets to break into coarse particles under specified conditions.
What are the types of tablets, and give one example for each?
- Uncoated tablets (e.g., standard ibuprofen)
- Coated tablets (e.g., film-coated aspirin)
- Effervescent tablets (e.g., Alka-Seltzer)
- Dispersible tablets (e.g., pediatric paracetamol)
- Orodispersible tablets (e.g., ondansetron)
- Gastro-resistant tablets (e.g., omeprazole)
- Modified-release tablets (e.g., metformin ER)
What forces affect tablet formation during compression?
- Axial force
- Radial force
- Attrition force
Effects: Reduces pore size, increases mechanical strength, and reduces disaggregation tendency.
Why is flowability important in tablet manufacturing?
Good flowability ensures uniform die filling and consistent tablet weight.
