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Gary's lecture (Pharmaceutics) > Pharmaceutical suspensions > Flashcards

Pharmaceutical suspensions Flashcards

1
Q

Provide examples of liquid and semi-solid dosage forms?

A
  • Solutions
  • Supsensions
  • Ointments
  • Creams
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2
Q

What are suspensions?

A

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

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3
Q

What is the dispersed phase in most pharmaceutical applications?

A

-Usually aqueous media or it may infrequently be an organic or oily material

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4
Q

Why do we need suspensions?

A
  • When drug is predominately insoluble
  • Drugs are more stable in a suspension or an emulsion than in another dosage form (stability)
  • There may be need to control the rate of release of the drug
  • When drug has bad taste if taken orally (compliance)
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5
Q

What are the different types of suspensions and provide examples for each?

A
  • Oral suspensions e.g Alumminium hydroxide
  • Parenteral suspensions e.g insulin zinc suspension
  • Topical suspensions - e.g Calamine lotion
  • Dry powder for suspensions e.g Barium sulphate suspension
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6
Q

What are the desirable properties of suspensions?

A
  • The dispersed particles should settle slowly (this allows for accurate and unifromity dose to be taken from medicine
  • The particles should remain flocculated (evenly distributed throughout the liquid media and should readily dispersed upon shaking)
  • Caking should be avoided - for uniformity of drug distribution and physical stability
  • Ease of use - viscosity should be appropriate
  • Particle size - should remain reasonably constant, this assists stability and re-dispersion
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7
Q

Controlling particles size controls what?

A
  • Texture
  • Dose uniformity
  • Variable dissolution and bioavailability
  • Sedimentation
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8
Q

Partciles will fall under the force of gravity according to stokes law. TRUE OR FALSE?

A

TRUE

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9
Q

According to stoke’s law, what physical properties influence sedimentation?

A
  • particle size

- Viscosity

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10
Q

What causes powders to float on top of a liquid?

A
  • Due the presence of an abosrbed layer of air
  • The lipophilic nature of certain materials or contamiants
  • Poor properties of wettability - referes to contact angle of particles and the surface
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11
Q

Hydrophobic powders have a high contact angle, they are not easily wetted and tend to float on the surface of the liquid. TRUE OR FALSE?

A

TRUE

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12
Q

Provide two examples of hydrophobic powders?

A
  • Sulphur

- Magnesium stearate

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13
Q

Hydrophilic powders tend to have low contact angle. TRUE OR FALSE?

A

TRUE

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14
Q

Hydrophilic powders are readily wettable. TRUE OR FALSE?

A

TRUE

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15
Q

Give two examples of hydrophilic powder?

A
  • Zinc oxide

- Magnesium carbonate

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16
Q

How to the addition of wetting agents improve particle wetting?

A

-They improve the wettability of hydrophobic powders by reducing surface tension between the particle and the liquid surface as well as reducing surface contact angle

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17
Q

Only wettable and wetted particles can be readily dispersed into the liquid and remain adequately dispersed. TRUE OR FALSE?

A

TRUE

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18
Q

Give examples of surfactants used in oral and i.v route in improving particle wettability?

A
  • Oral - the use of tweens and spans

- I.V - Lecithin and polysorbates

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19
Q

What is one disadvantage that comes with using surfactants for oral and i.v route to improve particle wettability?

A
  • They may cause excessive foaming in the product
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20
Q

Provide examples of hydrophilic colloids that are used to improve particle wettability?

A

-Acacia,bentonite

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21
Q

Particles that are intended for suspension generally do not become more wettable after being coated with a layer of hydrophilic colloid. TRUE OR FALSE?

A

FALSE

22
Q

Hydrophilic colloids also acts as suspending agents, as a result of their viscosity. TRUE OR FALSE?

A

TRUE

23
Q

Give examples of solvents used to improve particle wettability?

A
  • Various alcohols (ethanol)

- Glycerol, glycols

24
Q

What is the IUPAC definition for flocculation?

A

It is a process of contact and adhesion whereby the particles of a dispersion form large size clusters

25
Q

What does flocculation describe?

A

-The removal of a sediment from a fluid

26
Q

Flocculation cannot be forced through agitation or through the addition of flocculating agents. TRUE OR FALSE?

A

FALSE

27
Q

What are occurs in a deflocculated systems?

A

Deflocculated system:

  • Particles remain independent
  • Particles settle at different rates but overal slowly
  • Supernants remain turbid for a long time (small particles settle slowly)
  • Settled particles may form hard cake which is deifficult ot redisperse
28
Q

What occurs in a flocculated system?

A
  • Particles link together to form a loose structure
  • Big and small particles settle together in the loose structure
  • Supernants quickly become clear, different sizes link and settle together
  • The sediment remains loose, easy to redisperse
29
Q

Viscosity can be increased to reduce the rate of suspension. TRUE OR FALSE?

A

TRUE

30
Q

In storage a high viscosity can make product difficult to redisperse. TRUE OR FALSE?

A

TRUE

31
Q

A compromise between viscosity, degree of flocculation and ease of resuspension is not the normal solution. TRUE OR FALSE?

A

FALSE

32
Q

A bigger value of B, means the better flocculation. TRUE OR FASLE?

A

TRUE

33
Q

What does zeta potential describe?

A
  • It describes the electrical potential in the interfacial double layer at the boundary of different regions
34
Q

What is the zeta potential?

A
  • It is the potential difference between the dispersion medium and the stationary layer fluid attached to the dispersed particle in the suspension
35
Q

The concentration of the electrolytes is important in maintaining the stability of the suspension. TRUE OR FALSE?

A

TRUE

36
Q

What can occur if the conentration of the electrolytes is too high?

A
  • It may result in charge repulsion and caking of the suspended agent
37
Q

How can the concentration of the electrolytes be balanced?

A
  • by buffering the formulation to control pH and ionisation and electrolyte concentration
38
Q

Polymers cannot act as flocculating agents. TRUE OR FALSE?

A

FALSE

39
Q

Give an example of polymer used as a flucculating agent?

A
  • Starch

- cellulose derivatives

40
Q

Provide examples of viscosity modifiers?

A
  • Polysaccharides e.g acacia
  • Alginates
  • Water soluble cellulose
  • Carbomers
  • Hydrated silicates
41
Q

What other additives are added to suspensions?

A
  • Buffering agents
  • Sweetners
  • Flavours
  • Colouring agents
  • Preservatives
42
Q

Provide 4 ways in which suspensions can be manufactured?

A
  • Extramporaneous
  • High shear mixers
  • Homogenisers
  • Ball mills
43
Q

What is ostwald ripening?

A

It is the change of an inhomogenous structure overtime

44
Q

Suspensions contain particles suspended in saturated or supersaturated solutions of the drug substance. TRUE OR FALSE?

A

TRUE

45
Q

In such a system, small particles will tend to dissolve and large particles will tend to get larger. TRUE OR FALSE?

A

TRUE

46
Q

The solubulity of the particles do not depend on their particle size. TRUE OR FALSE?

A

FALSE

47
Q

What is polymorphism?

A

-Substances can exist in more than one crystal form

48
Q

Solubility can differ between polymorphs of the same material. TRUE OR FALSE?

A

TRUE

49
Q

Various polymers will form a protective layer around the particles. TRUE OR FALSE?

A

TRUE

50
Q

Most surfactants will reduce crystallisation but a few ight increase it. TRUE OR FALSE?

A

TRUE

51
Q

Temperature does not influence solubility and this can change the degree of saturation or supersaturation in solution. TRUE OR FALSE?

A

FALSE

52
Q

Provide the formulation for Calamine lotion ?

A
  • Calamine 30g
  • Zinc oxide 10g
  • Bentonite 6g (thickening agent)
  • Sodium citrate 1g (controls flocculation)
  • Liquified phenol 0.5ml (preservative)
  • Glycerol 5ml (thicknening)
  • Water 200ml

Gary's lecture (Pharmaceutics) (7 decks)

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