D8 and D9- Medicine design and manufacturing (emulsions, creams and ointments)

Question 1

what is an emulsion?

Answer 1

A liquid medicine in which one insoluble liquid is
dispersed as microscopic globules in another
liquid (the two liquids are ‘immiscible’)

Question 2

what is the external or continuous phase in an emulsion?

Answer 2

liquid vehicle

Question 3

what is the internal or dispersed phase in an emulsion?

Answer 3

droplets- there is Molecular film of emulsifying
agent(s) at the oil/water interface

Question 4

what are the different types of emulsion?

Answer 4

-o/w ‘Oil in Water’: Milky white
-w/o ‘Water in Oil’: Translucent
-w/o/w and o/w/o multiple emulsions: Droplets within
the droplets
pictures on one note!

Question 5

what types of oils are used in emulsions?

Answer 5

natural oils, mineral oils, volatile oils

Question 6

Describe natural oils

Answer 6

Triglycerides- e.g Vegetable oils (sunflower, olive, sesame)
Fish oil (cod liver oil)

Question 7

Describe mineral oils

Answer 7

Hydrocarbons
(petroleum industry)- e.g Liquid paraffin

Question 8

Describe volatile oils

Answer 8

Complex mixtures- e.g Plant oils- used as flavour and aromas (peppermint,
lemon)

Question 9

what is the issue with emulsions?

Answer 9

-stability
-two liquids separate- emulsions are physically unstable. creaming and cracking occur (one note for diagram)

Question 10

what is creaming?

Answer 10

Droplets coalesce
Oil collect near surface

Question 11

what is cracking?

Answer 11

complete phase separation

Question 12

how to prevent creaming and cracking through droplet size?

Answer 12

-Small droplets = more stable.
-Industry uses high shear mixers for small droplets
-Shelf-life: up to 2 years
Impossible with hand-made emulsions!
-Shelf-life: very short!

Question 13

how to prevent cracking and creaming through temperature?

Answer 13

-High risk if exposed to heat or temperature
fluctuations
→ Label: ‘Store in a cool place’
Freezing/thawing causes rapid separation (crystals)
→ Label: ‘Do not freeze’

Question 14

which kind of emulsion is more stable

Answer 14

o/w more stable than w/o (immediate cracking with w/o)

Question 15

are creams or liquid emulsions more stable?

Answer 15

creams

Question 16

what are Emulsifiers
(surfactants)?

Answer 16

‘surface active’ long molecules that locate at
the oil-water interface

Question 17

what are emulsifiers? (structure?)

Answer 17

-amphiphiles
-a hydrophilic head and hydrophobic tail
-position themselves at interfaces (diagram on one note)

Question 18

what are the types of emulsifiers

Answer 18

anionic, cationic, non- ionic
(charged can react with other charged species and be inactivated) (non- ionic more compatible with charged)
one note for diagram

Question 19

what other stability issues are with o/w emulsions? (sensitivity)

Answer 19

• The internal phase has a huge surface area
  → very sensitive to hydrolysis and fat oxidation (ester bonds hydrolyse and unsaturated bonds oxidise)
  → oil soluble antioxidant often needed
  -this leads to ‘rancidity’ (bad smell, change in appearance/ taste)
  look one one note

Question 20

what other issues are with o/w emulsions? (water)

Answer 20

• The continuous phase is water
  → microorganisms grow well in continuous phase
  (feed on the oil droplets!)
  → a preservative must be added BUT can destabilise the emulsifier film
  can partition into the oil – will be ineffective

Question 21

How unstable are emulsions?

Answer 21

physically, chemically and microbiologically unstable

Question 22

what are the uses of emulsions?

Answer 22

oral route and topical route

Question 22

Describe the oral route of emulsions

Answer 22

administer oils or oil soluble drugs by mouth
* More palatable
* Easier to administer (ex: feeding through nasogastric tube)
* More digestible due to large surface area of droplets

Question 23

Describe the topical route of emulsions

Answer 23

skin infections, inflammation,
allergy, etc…
-Lotions (runny): good to treat hairy or large areas
-Creams (semi-solid): less messy!

Question 24

what is a cream?

Answer 24

-An emulsion to be applied on the skin in which one of the two phases is a semi-solid or a wax (o/w or w/o) -may contain ingredients that are soluble either in oily or aqueous phase and insoluble powders

Question 25

what are the uses for o/w creams?

Answer 25

-Wounds, bites, acute inflammation, etc… -Can mix with wound exudates -Feels cool and dry the wound/skin (due to water evaporation) -Not greasy or sticky -Easy to rub onto the skin -Well accepted by patients

Question 26

what are the uses of w/o creams?

Answer 26

-‘oily’, so occlusive -Hydrate the skin (‘moisturising’) ex: Cold Cream BP -Protect against water (nappy rash, sunscreen) ex: Zinc Cream BP -not common as very unstable

Question 27

why do we use mixed emulsifiers? (charged and non- ionic)

Answer 27

-when using only charged amphiphiles, positive charges repel the interphase droplets and negative charges repel each other at interface creating a sparse interfacial film -mixed emulsifiers (charges and non- ionic) creates a dense interfacial film for better stability

Question 28

what is an ointment?

Answer 28

-Spreadable greasy semi -solids that might contain dispersed powders and small amounts of aqueous liquids -base is a mixture of waxes, fats, oils -hydrophobic -paste is an ointment with high powder content

Question 29

what are the stability issues with ointments?

Answer 29

-base is ONE greasy phase (can't separate) -do not contain water (microbial growth is limited, hydrolysis is unlikely) -can be sensitive to fat oxidation and light

Question 30

what are common ingredients in ointment bases?

Answer 30

-glycerides (mono, di or tri) -hydrocarbons (paraffins) -lanolin

Question 31

Describe hydrocarbons (paraffins)

Answer 31

-no reactive groups -chemically very stable -flammable

Question 32

Describe Lanolin

Answer 32

-yellow wax obtained from sheep wool -can cause allergic reaction

Question 33

What are the advantages of using ointments

Answer 33

-Occlusive → Make skin more supple (‘emollients’) → Suitable for dry skin conditions (ex: eczema) -Can be used in a bath (must contain emulsifiers) ex: Emulsifying Ointment BP -No preservatives needed → Suitable for patients with allergy

Question 34

Disadvantages of ointments?

Answer 34

-Very greasy → Stain clothes, difficult to rub onto or remove from the skin -Not very popular with patients! -Not suitable for wounds (increases temp and water content of skin, increasing risk of infection)

Question 35

what are the two main steps to prepare an ointment?

Answer 35

-Step 1: make the base by fusion -Step 2: disperse the powders manually by trituration

Question 36

How can you do trituration?

Answer 36

-On a tile – small amount of powder -In a mortar – large amount of powder

Question 37

How do you prepare the base?

Answer 37

-By fusion, i.e., melting and mixing over a steam bath -base ingredients are added in order of decreasing melting point (one note for diagram)

Question 38

How to disperse powders into base by trituration on a tile?

Answer 38

1. (Warm the tile) 2. Mix the powders on the tile 3. Add a portion of base similar to volume of powders 4. Using an ointment spatula, disperse the powders into the base by side to side smearing 5. Keep adding the base (one note for diagram)

Question 39

How to pack ointments and creams elegantly in a jar?

Answer 39

-flat surface -clean rim -shiny and clean jar -add labels

Question 40

How to assess the quality of your ointment?

Answer 40

-Any lumps? -Are the powders evenly mixed? -Is it gritty? (use greaseproof paper) -Is it elegantly packed in the jar? -Is the jar shiny and not greasy?

Question 41

How to prepare o/w cream?

Answer 41

-dissolve water soluble ingredients in aqueous phase -dissolve oil soluble ingredients in the melted oily phase -warm both to the same temp (melting point of oily phase) -mix while stirring (with glass rod until cold)

Question 42

how to make o/w creams to the final weight?

Answer 42

-issue is that water evaporates during warming → Lukewarm water must be added up to the final weight at the end (weigh evaporating dish before starting!)

Question 43

How to assess the quality of your o/w cream?

Answer 43

-Any sign of separation? -Any lumps? -Is it shiny (means the droplets of dispersed phase are small) -Is it elegantly packed in the tube ?