Excipients

Question 1

are excipients therapeutically active / unactive?

Answer 1

therapeutically unactive

Question 2

what do excipients control the behaviour of?

Answer 2

dosage form

e.g. can affect bioavailability

Question 3

what are the main properties of tablets?

Answer 3

• facilitate administration
• promote consistent drug release/bioavailability
• protect drug against degradation

Question 4

examples of tablet excipients?

Answer 4

• diluents/bulking agents
• lubricants
• binding agents
• glidants
• disintegrating agents
• dyes and flavouring agents
• coatings

Question 5

why are diluents/ bulking agents used?

Answer 5

added to make adequate sized tablets

Question 6

what is the most common bulking agent?

Answer 6

alpha lactose monohydrate

Question 7

properties of diluents/bulking agents?

Answer 7

• pleasant tase
• good solubility / dissolution
• low hygroscopicity
• inert

Question 8

what is spray dried lactose used for?

Answer 8

direct compression

Question 9

what is microcrystalline cellulose good for?

Answer 9

direct compression

Question 10

what is mannitol used for?

Answer 10

chewing tablets

Question 11

what is the function of lubricants?

Answer 11

• prevent powder/metal adherence
• ensures smooth ejection from die
• enhances flow properties

Question 12

example of a lubricant?

Answer 12

magnesium stearate (up to 1% w/w - hydrophobic)

Question 13

disadvantage of lubricants?

Answer 13

• prolongs disintegration time
• -> reduces drug dissolution
• reduces tablet strength

Question 14

is sodium stearyl fumarate hydrophilic / hydrophobic?

Answer 14

hydrophilic

Question 15

function of binding agents?

Answer 15

adhesives to bind particles together during granulation / as solution for wet granulation

Question 16

examples of binding agents?

Answer 16

• starch

- PVP (polyvinylpyrrolidine)

Question 17

function of glidants?

Answer 17

• improve flow of powders/granules

- reduces inter particulate friction - smooths surface irregularities

Question 18

example of glidant?

Answer 18

colloidal silica

Question 19

function of disintegrating agents?

Answer 19

• cause tablets to disintegrate —> inc surface area

Question 20

what do disintegrating agents do when in contact with water?

Answer 20

• swell

- burst open in water

Question 21

examples of disintegrating agents?

Answer 21

• starch

- croscarmellose sodium

Question 22

some disintegrating agents work by capillary action, which involves drawing liquid up through pores.

what does this do?

Answer 22

disrupts bonds between particles

e.g. pregelatinised starch

Question 23

lyophilised tablets take how long to disintegrate (orodispersible tablets)?

Answer 23

5 seconds

mainly sucrose

Question 24

what do coatings include?

Answer 24

• film / sugar coat
• enteric coatings (e.g. cellulose acetate phthalate / polymers- eudragits)
• polymers for M/R release e.g. HPMC and xanthan gum

Question 25

what are the excipients used for liquid prep?

Answer 25

- water - water miscible co solvents - buffers - antimicrobial agents - anti-oxidants - wetting agents - antifoaming agents - thickening agents - sweetening agents - flavouring agents - humectants

Question 26

water

Answer 26

- most used - physiologically non toxic and compatible - good dissolver

Question 27

what are the disadvantages to using water?

Answer 27

- supports microbial growth | - care with drugs prone to hydrolysis

Question 28

water miscible co solvents

Answer 28

- enhance solubility, taste and stability | - e.g propylene glycol, glycerol and ethanol

Question 29

buffers

Answer 29

- control pH - enables physiological compatibility, microbiological and chemical stability and solubility - OR INSOLUBILITY if taste = issue

Question 30

antimicrobial agents

Answer 30

- are preservatives | - prevent growth of opportunistic microbes (from excipients / externally introduced)

Question 31

anti-oxidants

Answer 31

- control oxidation of drug, preservative and excipients | - conc decreases with time since oxidises first

Question 32

wetting agents

Answer 32

- decrease interfacial tension - e.g. surfactants (cetrimide, SLS) - hydrophilic colloids (cellulose derivatives, tragacanth - also acts as suspending agent)

Question 33

antifoaming agents

Answer 33

e.g. simethicone

Question 34

thickening agents

Answer 34

- stabilise suspensions - give high viscosity (mostly thixotropic) e. g. methylcellulose

Question 35

sweetening agents

Answer 35

natural - sucrose | artificial - saccharin

Question 36

flavouring agents

Answer 36

natural - peppermint | artificial - butterscotch

Question 37

humectants

Answer 37

- hygroscopic excipients for external prep (suspensions, emulsions) e.g. glycerol, PEGs - reduce evaporation of water / aq vehicle —> prevents drying after application AND during product life

Question 38

what is the best lubricant?

Answer 38

magnesium stearate

Question 39

how long can sugars take to disintegrate?

Answer 39

up to an hour

Question 40

substances that contain more magnesium stearate means what..

Answer 40

higher disintegration time

Question 41

if a tablet is brittle what happens?

Answer 41

will fragment and break e.g. lactose