Dosage forms 2

Question 1

Disperse system

Answer 1

• One phase (a disperse phase) is distributed throughout a second phase (a continuous phase or dispersant)
• Two immiscible phases in contact

Question 2

Solutions

Answer 2

• Dissolving a solute into a solvent
• Molecular dispersion
• Contain small particles (ions or molecules)
• Transparent
• Do not separate
• Cannot be filtered
• Do not scatter light

Question 3

Disperse systems

Answer 3

• One phase (a disperse phase) is distributed throughout a second phase (a continuous phase or dispersant)

Question 4

Solutions examples

Answer 4

• Saline solution
• Multi-purpose contact lens solutions
• Hydrogen peroxide contact lens solutions

Question 5

Disperse systems examples

Answer 5

• Droplets of pine oil containing dissolved active germ‐killing ingredient (para‐chloro‐meta‐xylenol or PCMX), held dispersed in water by a layer of surfactant molecules

Question 6

What are colloids?

Answer 6

• A colloid or colloidal dispersion = a two-phase system of matter; a type of mixture intermediate between homogeneous mixtures and heterogeneous mixtures (size < 1 μm)
• In a phase colloid, small droplets or particles of one substance (the disperse phase) are dispersed in another (the continuous phase)
  In a molecular colloid, macromolecules are dispersed in a continuous phase

Question 7

Properties of colloids:

Answer 7

• Tyndall effect
• Brownian motion
• Adsorption
• Dialysis
• Electrophoresis
• Thixotropy

Question 8

Tyndall effect

Answer 8

• Colloids scatter light
• Light beam path through colloid is visible due to light scatter

Question 9

Brownian motion

Answer 9

• Under a microscope, the molecules of the liquid are in motion
• Because of the motion, the larger particles of the colloid are being constantly bombarded by the smaller particles of the liquid
• This motion and bombardment keeps the colloid particles suspended

Question 10

Adsorption

Answer 10

• A chemical is associated to the surface of a second agent
  Often reversible
• Can lead to conformational changes
• Manipulate physicochemical properties
• Examples:
  Adsorption of gases on solids
  Adsorption of surfactants, polymers or proteins

Question 11

Dialysis

Answer 11

• Separation of suspended colloidal particles from dissolved ions or molecules of small dimensions
• By means of their unequal rates of diffusion through the pores of semi-permeable membranes

Question 12

Process of Electrophoresis

Answer 12

• Migration of charged particles
• Surface dependent

Question 13

Thixotropy

Question 14

Types of colloids

Answer 14

1. Gas
2. Liquid
3. Solid

Based on nature of the interaction between the dispersed phase and the continuous phase:
4. Lyophobic
5. Lyophilic

Question 15

How to distinguish between a solution and a colloidal dispersion?

Question 16

Three types of colloids:

Answer 16

1. Sol (Gel)
2. Foam (Defoamer)
3. Emulsion

Question 17

Lyophobic

Answer 17

Solvent hating (hydrophobic when the solvent is water)

Question 18

Lyophilic

Answer 18

Solvent liking (hydrophilic when the solvent is water)

Question 19

Properties of lyophobic

Answer 19

• Inorganic molecules or particles (insoluble)
• Little or no interaction between particles and dispersion medium
• Do not disperse spontaneously, special procedures needed
• No effect on viscosity unsolvated
• Electrolytes: low concentrations may stabilise,
  higher concentration causes instability

Question 20

Example of lyophobic colloids

Answer 20

Calcium phosphate

Question 21

Lyophilic

Answer 21

• Large organic molecules in colloidal size range
  Solvated by medium (H2O – this is hydrated)
• Disperse spontaneously
• Increase viscosity, forming gels at higher concentrations
• Electrolytes: generally stable but “salted out” by very high concentrations due to desolvation

Question 22

Examples of Lyophilic colloids

Answer 22

• Starch
• Gelatin

Question 23

Particles in colloids, how big?

Answer 23

Less than 1 um (micrometer)

Question 24

Colloids - Sol

Answer 24

a colloidal suspension of small solid particles in a continuous liquid medium

Question 25

Colloids - Gel

Answer 25

- a colloidal suspension in which the liquid medium has become viscous enough to behave more or less as a solid - Solid particles will arrange themselves into a 3D structure within the liquid solvent, giving the solution a rigid, definite shape as in a jelly

Question 26

Examples of Gels

Answer 26

1. Nail polish 2. Styling gel 3. Eye gel

Question 27

Examples of PHARMACEUTICAL Gels

Answer 27

1. Aloe Vera gel 2. 'Burncare' - relieve burn gel 3. Ibuprofen Gel

Question 28

Gels: what phase?

Answer 28

1. Lyophobic - two-phase system 2. Lyophilic - one-phase system

Question 29

Lyophobic - two-phase system

Answer 29

a) Flocculated particles in a two-phase gel structure b) Network of elongated particles or rods forming a gel structure

Question 30

Lyophilic - one-phase system

Answer 30

c) Matted fibres as found in soap gels d) Crystalline and amorphous regions in a gel of carboxymethylcellulose

Question 31

Gels formulation:

Answer 31

Gelling agents: -natural gums (tragacanth, carrageen, pectin, agar, alginic acid) -Semisynthetic material -synthetic Humectants; prevent drying out (glycerol, sorbitol) -preservatives -water

Question 32

Whats are foams?

Answer 32

Gases dispersed in a liquid/solid - formed by trapping many gas bubbled

Question 33

What are foams normally used for?

Answer 33

Delivery of enemas and topical drugs

Question 34

Why are foams sometimes troublesome in manufacture?

Answer 34

Produced as UNWANTED by-products (if foam forms on shaking)

Question 35

What instructions/directions are common when using foams?

Answer 35

Shake well before use

Question 36

Defoamers/ antifoaming agents:

Answer 36

Foam breakers and preventers - Act as small droplets forming in the foam lamellae - Displaces surfactants (which stabilise the thin films) at the air-water interface

Question 37

Example of a defoamer

Answer 37

Silicone fluids

Question 38

Emulsions

Answer 38

A ‘pseudo-stable’ dispersion of at least two immiscible liquids, one of which is dispersed throughout the other in the form of fine droplets (generally oil and water) stabilised by the presence of an emulsifying agent (known as emulsifier

Question 39

Suspensions (not a colloid)

Answer 39

Course dispersion in which insoluble particles, generally > 1 μm, are dispersed within a liquid medium which is usually aqueous

Question 40

Directions to use suspensions

Answer 40

1. Settle out 2. Shake to stay suspended

Question 41

solution v colloid v suspension

Answer 41

Consider properties: 1. particle size 2. appearance 3. separation 4. filtration 5. effect of light 6. visibility

Question 42

Sizes

Answer 42

Solution : less than 10^-9 Colloid : less than 10^-6 Suspension : more than 10^-6