Keele Suspensions

Front 1

What is a suspension (by definition)?

Back 1

A coarse disperse system where an insoluble solid is dispersed in a liquid medium

Front 2

What is the disperse phase made of?

Back 2

Solid particles, usually > 0.1µm

Front 3

What is the disperse medium made of?

Back 3

Aqueous media

(Infrequently also organic or oil)

Front 4

What are the reasons for formulating a suspension?

Back 4

-Drug is predominantly insoluble

-Drug is more stable in suspension

-Need to control the rate of release of the drug

-Drug has bad taste> helps to improve compliance by masking taste

-Easy to swallow

-Can divide and control the dose

-Fast pharmaceutical action

Front 5

List some examples of oral suspensions

Back 5

Aluminium hydroxide or magnesium hydroxide antacid suspensions

Front 6

State an example of a parenteral suspension

Back 6

Insulin zinc suspension BP

Front 7

State an example of a topical application

Back 7

Calamine lotion BP

Front 8

State an example of dry powder for suspensions

Back 8

Barium Sulphate for suspension BP

Front 9

Why can prednisolone be put in suspension?

Back 9

It's poorly soluble

Front 10

Why is Oxytetracycline put in suspensions?

Back 10

To prevent degradation of drug/ to improve stability of the drug

Front 11

Why is Chloramphenicol Palmitate put in suspension?

Back 11

To mask the taste, it's bitter/unpleasant

Front 12

Why is calamine lotion put in suspension?

Back 12

For use as a topical applicant

Front 13

Why are penicillin and procaine put in suspension?

Back 13

To control the rate of drug absorption (Parenteral application)

Front 14

Give an example of a vaccine put in suspension

Back 14

Cholera vaccine

Front 15

Which x-ray contrast agent is formulated as a suspension?

Back 15

Barium Sulphate

Front 16

What are the desirable properties of suspensions?

Back 16

-Dispersed particles should settle slowly, allowing accurate and uniform dose

-The particles should remain flocculated and be readily dispersed upon shaking (caking/aggregation should be avoided)

-Ease of use: viscosity, product must be easily dispersed from its container

-Particle size: should remain reasonably constant to assist stability and re-dispersion

Front 17

What does particle size affect?

Back 17

-Dose uniformity

-Variable dissolution and bioavailability

-Sedimentation (physical stability)

-Texture (larger particles over 5µm in diameter give gritty texture)

Front 18

Which law do particles follow during sedimentation?

Back 18

Stoke's Law

Front 19

What is the sedimentation volume, F, defined as?

Back 19

The raito of the Height of the sediment/Height of the whole pharmaceutical product

Vu/Vo

Front 20

Why do powders float on top of liquids?

Back 20

-Presence of an absrobed layer of air

-The lipophilic nature of certain materials or contaminants

-Poor properties of "wettability"- this generally refers to the contact angle of the particle and the surface

Front 21

What are the properties of hydrophobic powders?

Back 21

-Have high contact angle

-Not easily wetted and tend to float on the surface of the liquid

(eg: sulphur or magnesium stearate)

Front 22

What are the properties of hydrophilic powders?

Back 22

-Low contact angle

-Readily wetted

(eg zinc oxide or magnesium carbonate)

Front 23

How can you improve particle wetting?

Back 23

Use wetting agents. This improves wettability of hydrophobic powders by reducing surface tension between the particle and the liquid surface, and therefore reducing the contact angle

Front 24

Why must particles be wetted for suspensions?

Back 24

Only wettable and wetted particles can be readily dispersed into the liquid and remain adequately dispersed

Front 25

Which wetting agents are used for oral suspensions?

Back 25

Surfactants such as polysorbates sorbitan esters (Tweens and Spans)

Front 26

Which wetting agents are used for IV suspensions?

Back 26

Lecithin, polysorbates and poloxamers and related materials

Front 27

In what concentrations are wetting agents used?

Back 27

Used in relatively low (ca. 0.1% w/w) concentrations

Front 28

What is a disadvanatge of wetting agents?

Back 28

They may cause excessive foaming in product

Front 29

What are some examples of hydrophilic colloids?

Back 29

Acacia, bentonite, tragacanth, alginates, xantham gum and carious celluose derivatives

Front 30

What are hydrophilic colloids used for?

Back 30

-Used to coat particles to make them more wettable

-Act as suspending agents due to their viscosity

Front 31

Which solvents are used to improve particle wetting?

Back 31

Various alcohols (usually ethanol), glycerol and glycols

Front 32

What are solvents used for in suspensions?

Back 32

To penetrate into loose aggregations of particles to displace the air adsorbed within such structures

Front 33

What is the definition of flocculation?

Back 33

A process of contact and adhesion whereby the particles of a dispersion form larger-size clusters

Front 34

What is flocculation?

Back 34

The removal of a sediment from a fluid. Flocculation can be forced through agitation or the addition of flocculating agents

Front 35

Flocculation vs Deflocculation

Back 35

Front 36

What is the equation for sedimentation volume in a deflocculated system?

Back 36

Fu = Vu/V0

Front 37

What is the equation for sedimentation volume in a flocculated system?

Back 37

Ff = Vf/V0

Front 38

What is the equation for the degree of flocculation?

Back 38

β = Ff/Fu = Vf/Vu

Front 39

What does a bigger value of β mean?

Back 39

Better flocculation

Front 40

What is Zeta potential?

Back 40

The electrical potential in the interfaical double layer at the boundary of different regions of a suspension. The potential difference between the dispersion medium and the stationary layer of fluid attached to the dispersed particle in suspension.

Front 41

What happens if the concentration of electrolytes in suspension is too high?

Back 41

Results in charge repulsion and therefore caking of the suspended agent

Front 42

How is flocculation in suspension controlled?

Back 42

By buffering the formulation to control the pH and ionisation, and by controlling the electrolyte concentration

Front 43

Which polymers are used in suspensions?

Back 43

Starch, alginates, tragacanth, and cellulose derivatives

Front 44

Give two examples of polysaccharides and when they're used

Back 44

-Acacia: used with other thickeners in extemporaneous products

-Tragacanth: used in extemporaneous products, slow to hydrate, and shows non-Newtonian behaviour

Front 45

List different types of viscosity modifiers

Back 45

-Polysaccharides

-Alginates

-Water-soluble celluloses

-Hydrated silicates

-Carbomers

Front 46

Why are hydrated silicates used to modify viscosity?

Back 46

They're highly absorbent and Non-Newtonian

Front 47

What additives are added to suspensions to improve compliance and shelf life?

Back 47

-Buffering agents

-Sweeteners

-Flavours

-Colouring agents

-Preservatives

Front 48

Which methods can be used to manufacture suspensions?

Back 48

-Extemporaneous methods eg: mortar and pestle

-High-shear mixers

-Homogenisers

-Ball mills

Front 49

What is the definition of Ostwald Ripening?

Back 49

The change of an inhomogeneous structure over time. Over time, small crystals (or sol particles) dissolve, and redeposit onto larger crystals or sol particles.

Front 50

What is the equation for the solubility of particles?

Back 50

Front 51

How many common crystal forms does cortisone acetate suspension have? How many of these are unstable, and how do they change into the stable form?

Back 51

Five common crystal forms

Four unstable> turn to stable form in presence of water

(caking is often observed when the crystal form changes)

Front 52

Which additives or conditions can cause the inhibition of crystal growth?

Back 52

-Polymers> form a prtoective layer around the particles

-Surfactants>reduce crystallisation (some may increase it)

-Temperature> influences solubility, which changes the degree of saturation or supersaturation in solution

Front 53

Which tests are carried out to evaluate physical stability?

Back 53

-Aesthetic tests (appearance, colour, odour, taste)

-pH (zeta potential and solubility)

-Sedimentation rate

-Particle size and form

-Redispersion and centrifugation tests

-Rheological measurements

-Freeze-Thaw temperature cycling

-Compatability with container and cap liner

-Dose uniformity

-Microbial testing

Front 54

What excipients are in calamine lotion, and why?

Back 54

-Calamine 30g

-Zinc oxide 10g-Bentonite 6g (thickening agent)-Sodium citrate 1g (controls flocculation)-Liquefied phenol 0.5mL (preservative)-Glycerol 5mL (thickening agent; also helps the product adhere better to the skin)-Water to 200mL