Oral powders

Question 1

why can you not just have drugs in the powder form?

Answer 1

usually too sticky as a powder so needs to mix with something else to make it a working tablet

Question 2

what does “powder” mean in pharmaceutics ?

Answer 2

As a dosage form:
“describes a formulation in which a drug powder has been mixed with other powdered excipients to produce the final product”

As a precursor of a dosage form:
Can be precursor of tablets either
- directly (compressed to form tablets)
- or indirectly (via granules)

Question 3

What does granules mean in pharmaceutics?

Answer 3

As a dosage form:
“granules as dosage forms are powder particles that have been aggregated to form a larger particle 2 to 4 mm diameter”

As a precursor of a dosage form:
Granules can also be an intermediate of tablet manufacturing

Question 4

What are advantages of powders/granules vs tablets/capsules/liquids?

Answer 4

• more stable in liquid
• convenient for large doses
• faster dissolution rate that capsule or tablet (material is already in powdered form - small particle sizes dissolve faster)

Question 5

what are disadvantages of powders/granules vs tablets/capsule/liquids?

Answer 5

• less convenient to carry than tablets/capsules
  -difficult to mask (unpleasant taste)
• not suitable for administration of potent drugs
• not suitable for drugs inactivated in the stomach or that can cause stomach irritation

Question 6

what are uses for powders and granules for pharmaceutical use orally?

Answer 6

• bulk powders or granules for internal use
• divided powders or granules (single preparations)

Question 7

what are other administration routes for powders and granules?

Answer 7

• dusting powders for external use
• insufflation (ear/nose/throat)
• antibiotic syrups to be reconstituted before use
• powders to be reconstituted into injections
• dry powder inhalers

Question 8

why is particle size so important ?

Answer 8

• Drug bioavailability
• settling rate (suspensions)
• possibility of obtaining homogenous mixtures
• flowability
• tolerability of some dosage forms

Question 9

what are the 4 different types of particle size distribution?

Answer 9

• Monosized distribution (very unlikely)
• normal distribution
• positively skewed distribution
• bimodal distribution

Question 10

how do you get the cumulative frequency of particles?

Answer 10

Equivalent particle diameter + percentage

Question 11

what are forces that favour the affect of powder flow?

Answer 11

Gravity (causes it to flow down)
True density of particles
Angle of surface over which particles are flowing

Question 12

what are the forces that are against powder flow?

Answer 12

Adhesion forces (particle and container) - might stick to walls
Cohesion forces (particles may become attached to each other )

Question 13

how does fine powders effect powder flow?

Answer 13

they have higher surface/mass ratio and therefore higher cohesion

Question 14

what shape particles flow easier?

Answer 14

spherical

Question 15

How can you measure flowability

Answer 15

Angle of repose

Powder is put through a funnel to form a cone shape

Want a low angle of repose for powder flow (non-cohesive)

Question 16

What is the bulk/apparent volume?

Answer 16

The volume occupied by a powder including the pores (ie. empty gaps between particles)

Question 17

What is the tapped volume?

Answer 17

volume occupied by a powder after tapping (tapped density test uses a powder in a measuring cylinder and machine is used to tap powder through to get weight and volume)

Question 18

what is the true volume?

Answer 18

The volume occupied by a powder excluding the volume occupied by the pores

Question 19

how do you calculate the bulk density?

Answer 19

Bulk density = mass/Vbulk

Question 20

how do you calculate the true density?

Answer 20

True density = mass / Vtrue

Question 21

What value is always less bulk density or true density?

Answer 21

bulk density

Question 22

how do you calculated the porosity?

Answer 22

1 - volume (particles) / volume of (bulk)

Question 23

what is porosity and why is it important?

Answer 23

• important not only in powders but tablets too
• measure of spaces between particles

Question 24

what does a high porosity mean?

Answer 24

water is able to move into the tablet more quickly to be dissolved quicker

Question 25

what is granulation?

Answer 25

the process in which homogenous mixtures of primary powder particles form larger, still homogeneous particles called granules (process of mixing powders)

Question 26

what are advantages of granulation?

Answer 26

1) improve powder flow
2) prevent segregation
3) improve compaction

Reduced generation of dust
Granules occupy less volume

Question 27

what is wet granulation?

Answer 27

Powders are mixed through with a granulating sieve and the mass is forced through a sieve
- popular with tablets that contain large amounts of drugs in it eg. paracetamol

Question 28

what is the wet granulation mechanism?

Answer 28

1) Adhesion and cohesion forces in immobile films
2) interfacial forces in mobile liquid films
3) solid bridges (hardening binders or crytallisation of dissolved substances)
4) attractive forces between particles

Question 29

what is the granulation mechanisms of dry granulation?

Answer 29

Attractive forces between solid particles
- solid bridges (by partial melting)

Question 30

what is the mechanism of dry granule formation?

Answer 30

• applied pressure
• formation of a sheet
• milling and sieving
• granules