oral powders

Question 1

powder as a dosage form meaning

Answer 1

describes a formulation in which a drug powder has been mixed with other powdered excipients to produce the final product

Question 2

meaning of a powder as a precursor of a dosage tablet

Answer 2

can be a precursor of tablets either
- directly (powder compressed to form a tablet)
- indirectly (via granules)

Question 3

what do granules mean as a dosage form

Answer 3

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

Question 4

granules as a precursor of a dosage form

Answer 4

granules can also be an intermediate of tablet manufacturing
(typically 0.2-0.5mm)

Question 5

advantages of powders and granules compared to tablets/capsules/liquids

Answer 5

• more stable than liquid
• convenient for large doses (1-5g)
• faster dissolution rate than capsules or tablets

Question 6

disadvantages of powders and granules compared to tablets/capsules/liquids

Answer 6

• 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 damage

Question 7

what powders and granules are used orally

Answer 7

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

Question 8

non oral administration routes of powders and granules

Answer 8

• dusting powders for external use
• insufflation (ear/nose/throat)
• antibiotic syrups
• powders for reconstitution into injections
• dry powders inhalers

Question 9

what can particle size affect

Answer 9

• drug bioavailability
• settling rate
• possibility of obtaining homogenous mixtures
• flowability
• tolerability of some dosage forms

Question 10

what factors favour powder flow

Answer 10

• gravity
• true density of particles
• angle of the surface over which particles are flowing

Question 11

what factors are against powder flow

Answer 11

• adhesion forces (particles and container)
• cohesion forces (particles-particles)

Question 12

why do fine powders have higher cohesion

Answer 12

because they have higher surface/mass ratio

Question 13

can particle shape affect the flow

Answer 13

yes

Question 14

how does angle of repose work

Answer 14

you put powder into a funnel and pour it out into a cone shape

a low angle of repose allows good powder flow

Question 15

what does it mean if theta is high (angle of repose)

Answer 15

the powder is cohesive

Question 16

what does it mean if theta is low (angle of repose)

Answer 16

powder is non cohesive

Question 17

what is bulk or apparent volume

Answer 17

the volume occupied by a powder including the pores

(ie the empty gaps between particles)

Question 18

what is the tapped volume

Answer 18

the volume occupied by a powder after tapping

Question 19

what is the true volume

Answer 19

the volume occupied by a power excluding the volume occupied by the pores

Question 20

formula for bulk density

Answer 20

mass / Vbulk

Question 21

formula for true density

Answer 21

mass / Vtrue

Question 22

is the bulk density of a powder less or more than the true density

Answer 22

less

Question 23

what is the K true density

Answer 23

the bulk density

Question 24

formula for bulk density

Answer 24

mass / Vbulk

Question 25

formula of true density

Answer 25

mass / Vtrue

Question 26

formula for K

Answer 26

bulk density / true density or Vparticles / Vbulk

Question 27

what is porosity

Answer 27

the (%) voidage of the powder bed

Question 28

what does high porosity mean

Answer 28

water can get into particles really quickly

Question 29

what are the 3 porosity formulas

Answer 29

Vpores / Vbulk or (Vbulk - Vparticles) / Vbulk or 1 - (Vparticles / Vbulk)

Question 30

what is granulation

Answer 30

the process in which homogenous mixtures of primary powder particles from larger particles called granules

Question 31

3 main advantages of granulation

Answer 31

1. improve powder flow 2. prevent segregation 3. improve compaction (ie tableting)

Question 32

other reasons for granulation

Answer 32

- reduce generation of dust (good for toxic compounds) - they retain flowability even after absorbing moisture - granules occupy less volume (good for storage)

Question 33

what are the types of granulation

Answer 33

- wet granulation - dry granulation

Question 34

wet granulation process

Answer 34

1. powders are mixed with a granulating fluid 2. the mass is forced through. sieve

Question 35

when would wet granulation be the usually favoured choice

Answer 35

when the tablets contain larger amounts of the drugs

Question 36

chemistry behind wet granulation

Answer 36

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

Question 37

dry granulation process

Answer 37

1. a pressure is applied 2. the intermediate product is broken 3. sieving

Question 38

chemistry of dry granulation

Answer 38

- attractive forces between solid particles - solid bridges formed by partial melting