emulsions cream and ointements

Question 1

what’s an emulsion

Answer 1

a liquid medicines where one insoluble liquid is dispersed as microscopic globules in another liquid

Question 2

continuous phase in emulsions

Answer 2

is the liquid vehicle

Question 3

dispersed phase

Answer 3

is the droplets

Question 4

types of emulsions

Answer 4

-oil in. water: milky white
-water in oil : translucent
-multiple emulsions: this droplets in droplets

Question 5

types of oils that can be used in emulsions

Answer 5

-natural oils: triglycerides (veg or fish oils)n

-mineral oils: hydrocarbons, liquid parafins

-volatlie oils: complexs mixtures eg. plant oils

Question 6

issues with emulsions

Answer 6

-physical stability

• the two liquids want to separate and this can lead to creaming (oil collects near the surprise) or cracking which is phase seperation

Question 7

how to prevent creaming and cracking

Answer 7

• control droplet size: small drops are usually more stable the industry makes small drops using shear mixers (up to two years shelf life) can’t do this with hand made emulsions hence why shelf life is very short

-tempreture: cool place is the best, fluctuation increases separations

-oil in water is more stable than water in oil

-use emulsifiers (surfactants): long molecules that are on the oil water interface

Question 8

emulsifiers structure

Answer 8

they at amphiphiles which mean they have a hydrophilic head and hydrophobic tail

Question 9

three types of emulsifiers

Answer 9

• anionic
  -cationic
  widely used but when they react with a charged species they become in active

-non ionic ( more compatible with charges ingredients)

Question 10

why is using mixed emulsifiers better

Answer 10

• single charged is good as they repel internal phase droplets however they repel each other on the surface so there is sparse coverage

-mixed emulsifiers means charged and non ionic means a dense interfacial film

Question 11

why we need antioxidants

Answer 11

-the internal phase has large surface are and is very sensitive to hydrolysis and fat oxidation so and oil soluble antioxidant is required

Question 12

why we need preservative

Answer 12

microorganisms grow well in water and feed on the oil droplets, preservatives can be added but then they can destabilise emulsifier film and partition into in to the oil

Question 13

different instabilities of emulsions

Answer 13

-physicially
-chemically
-microbiologically unstable

Question 14

uses of emulsions oral routes

Answer 14

-oral route: used to administer oils or oil soluble drugs, this is good because its : more palatable, easier to administer eg through feeding tubes and its more digestible to large surface area of droplets

Question 15

topical route of emulsions

Answer 15

used for skin infections, inflammations, allergy

-lotions (large areas)
-creams (less messy)

Question 16

whats a cream

Answer 16

an emulsions where one of the two phases is semi solid or wax

can contain insoluble powders and ingredients that are only soluble in the oil and aqueous phase

Question 17

o/w creams uses

Answer 17

• Wounds*,bites,acute inflammation, etc…
• Can mix with wound exudates
• Feels cool and dry the wound/skin
• Not greasy or sticky
• Easy to rub on to the skin
• Well accepted by patients

Question 18

w/o cream uses

Answer 18

‘oily’, so seals off areas
* Hydrate the skin
(‘moisturising’)
ex: Cold Cream BP
* Protect against water (nappy rash, sunscreen)
ex: Zinc Cream BP

super unstable tho

Question 19

what is ointments

Answer 19

Spreadable greasy semi-solids that might contain dispersed powders and small amounts of aqueous liquids

The base is a uniform mixture of waxes, fats and oils
→ hydrophobic, so water repellent

Question 20

paste

Answer 20

An ointment with a high powder content is called a paste

Question 21

Stability issues with ointment bases

Answer 21

Notmany!
* 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 22

Common ingredients in ointment bases

Answer 22

-glycerides

-Lanolin: yellow wax obtained from sheep wool ( can cause allergic reactions)

-hydrocarbons: no reactive groups meaning they are very chemically stable

Question 23

advantages of using ointments

Answer 23

-occlusive (seals off areas)
-makes skin more supple
-suitable for dry skin conditions
-can be used in bath
-no preservatives needed so its suitable for patients with allergy

Question 24

disadvantages of ointments

Answer 24

-very greasy
-stain
-difficult to rub or remove of skins
-not suitable for wounds

Question 25

how to prepare the base

Answer 25

By fusion, i.e., melting and mixing over a steam bath

BASE INGREDIENTS are added in order of decreasing melting point