Liquid Formulations

Question 1

what are some common solvents

Answer 1

water
alcohol
glycerol (glycerine)
propylene glycol

Question 2

what are some excipients in solvents

Answer 2

buffers
sweetening agents
viscosity enhancement
preservatives
reducing agents/antioxidants
flavours and perfumes 
colours
density modifiers
isotonicty modifiers

Question 3

what are buffers

Answer 3

buffers control the pH of the pharmaceutical preparation

common buffers for pharmaceutical solutions are:
phosphate,citrate and acetate buffers

Question 4

what do you need to achieve a buffer

Answer 4

acid + base to achieve the buffering

Question 5

what is the sweetening agents used for

Answer 5

increase palatability of the API / Preparation

Question 6

what are some commonly used sweetening agents

Answer 6

sucrose
sorbitol
mannitol
na and ca salts of saccharin
glycerol
aspartame

Question 7

what are viscosity enhancement

Answer 7

hydrophilic polymers are commonlu used for viscosity enhancement

Question 8

what do preservatives do

Answer 8

control microbial growth

Question 9

what do antioxidants use

Answer 9

enhances stability of the API have higher oxidative potential than API or inhibit free radical induced decomposition

Question 10

what are the advantages of solutions

Answer 10

easy to swallow

fast therapeutic response immediately available for absorption

homogeneous

minimal irritation to gastric mucosA

Question 11

what are the disadvantages of solutions

Answer 11

bulky
poorer stability in solution
microorganisation growth preservative needed
issues with accuracy of dose
taste is pronounced

Question 12

What are the uses of emultions

Answer 12

predominantly topical

IV
Rectal
Oral

Question 13

what are the desired characteristics of an emulsions

Answer 13

physical stability - no separation
should be easily remove from container and applied
pleasant texture; aesthetically pleasing

Question 14

what is an emulsion

Answer 14

Anemulsionis mixture of two liquids that would not normally mix, i.e. a mixture of two immiscible liquids. Bydefinition, anemulsioncontains tiny particles of one liquid suspended in another. Chemically, they are colloids where both phases are liquids.

Question 15

what are the different types of emulsions

Answer 15

o/w for oral and i.v.

Both o/w and w/o for topical; w/o more greasy formulation but more hydrating to the skin

Multiple emulsions – o/w/o or w/o/w

Question 16

what are the advantages of emulsions

Answer 16

deliver drugs of low aqueous solubility

making taste - flavours added to external phase whilst drug is in the internal phase

employed for total parental nutrition

good for patients with swallowing difficulties

Question 17

what are the disadvantages of emulsions

Answer 17

fundamentally unstable

may be difficult to manufacture

Question 18

what is the name of the phase that is disperced into the medium

Answer 18

immiscible phase

Question 19

what has the lowest surface area per volume

Answer 19

droplets

Question 20

what does dispersion lead to

Answer 20

high surface area of the dispersed phase

Question 21

how can we avoid creaming of our emulsion

Answer 21

Reduced droplet size – Smaller droplets flocculate slower!

Increase viscosity (of continuous phase) – make it harder for the droplets to move!

Reduced density difference between phases – Lower difference gravity effects are lowered!

Disperse phase concentration – Lower dispersed phased concentration, slower coalescence.

Prevention of flocculation and coalescence – Additives to reduce creaming.

Question 22

how can we use surfactants

Answer 22

Amphipathic nature of the surfactant means they are present at the phase boundary

Surfactants keep the droplet size small, hence aid dispersion and stability

Coalescence is prevented by the steric repulsion

Mainly non-ionic surfactants employed for internal use; charged surfactants for skin preparations

Question 23

use of hydrophilic polymers

Answer 23

Use of hydrophilic polymers – these adsorb at the interface of the phases producing multilayers
The multilayers are highly viscoelastic, so mechanically prevent coalescence
If ionic hydrophylic polymers are used, zeta potential is created – further stability