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MPharm 2 - PH2107 > Unit 2 - Rectal delivery 2 > Flashcards

Unit 2 - Rectal delivery 2 Flashcards

1
Q

What are the ideal properties of a suppository base?

A
  • rapid release of drug in active form
  • patient acceptability
  • ease of manufacture
  • stability during storage (fatty bases)
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2
Q

Why is rapid release of drug active form in a suppository important?

A
  • either melts at body temperature or dissolve in rectal fluids to release drug within 10 minutes
  • compatibility with a broad variety of drugs (no chemical reaction or complex formation)
  • good wetting, emulsifying properties
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3
Q

What factors are important for patient acceptability in suppositories?

A
  • neither toxic, sensitising, nor irritant to rectal mucosa
  • capable of being handled and firm enough for easy application
  • bland
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4
Q

What factors are important for manufacturing suppositories?

A
  • easily moulded by pouring
  • adequate shrinkage allowing easy removal from mould without lubricant
  • good suspending power for heavy insoluble medicaments
  • stable above melting point
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5
Q

What can higher melting point suppository bases be used for?

A 
Drugs that lower the melting point of the base
- camphor
- chloral hydrate
- menthol
- phenol
- thymol
- volatile oils
Or when formulating suppositories in tropical climates
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6
Q

When can lower melting point suppository bases be used?

A

When adding materials that will raise the melting points or if adding large amounts of solids

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7
Q

What are the two methods in preparing suppositories?

A
  • moulding

- compression

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8
Q

How are suppositories moulded?

A
  • melt base
  • incorporate ingredients
  • pour into mould (overfill)
  • allow to cool
  • remove from mould
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9
Q

Give examples of suitable bases that can be used to make suppositories

A
  • cocoa butter
  • hard fats
  • glycerinated gelatin
  • PEGs
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10
Q

Describe suppository moulds

A
  • commonly made from metal or plastic
  • care must be taken in cleaning and drying
  • lubrication may be required (glycerinated gelatin)
  • calibration may be required
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11
Q

How are suppository moulds calibrated?

A
  • pour base into mould
  • cool and trim
  • remove suppository and weigh
  • divide total weight by the number of blank suppositories prepared to obtain the average weight of each suppository for this particular base
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12
Q

How is the melt prepared for a suppository base?

A
  • use the least possible heat
  • incorporate medicament
  • pour close to congealing point
  • pour continuously to avoid layering
  • overfill mould
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13
Q

How is the drug prepared for a suppository?

A
  • comminuted to a uniform, small particle size
  • maximum quantity of drug/excipient to be incorporated is 30% of the blank weight of the suppository
  • liquids may occupy too much volume to be easily incorporated
  • if a large quantity of liquid is to be incorporated into an oily suppository base, a water-in-oil emulsion may be required
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14
Q

How is a drug be mixed and poured to make a suppository?

A
  • sufficient mixing to obtain a uniform distribution of the drug
  • slowly fill cavity, avoiding air bubbles, leaving a small excess of material on the top of the mould
  • do not stop the pouring process until the mould is filled
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15
Q

How are suppositories cooled and finished?

A
  • set at room temperature or by refrigeration (if necessary)
  • remove excess material to leave a nice smooth surface on the suppository
  • remove carefully from the mould, package and label
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16
Q

How are suppositories compressed?

A
  • incorporate ingredients vigorously
  • force into mould using compression machinery
  • remove from mould
17
Q

What is compression manufacture of suppositories suitable for?

A
  • bases that can be formed into suppositories under pressure

- useful for heat labile medicaments and where there is a large amount of insoluble material

18
Q

What are the limitations in compression manufacture of suppositories?

A
  • special machinery required
  • limitation to suppository shape
  • air entrapment
  • slow
19
Q

What are the problems in suppository preparation?

A
  • moisture in suppositories
  • hygroscopicity
  • incompatibilities
  • viscosity
  • brittleness
  • volume contraction
  • rancidity
20
Q

Why should water be avoided in suppositories?

A
  • accelerates oxidation of fats
  • crystallises materials on evaporation
  • increases reactions between ingredients
  • assists bacterial growth
21
Q

Why is hygroscopicity a problem in suppositories?

A

Irritable for patient

22
Q

Why is viscosity important in suppository manufacture?

A
  • controls sedimentation

- control temperature or add viscosity enhancer e.g. aluminium monostearate or increase fatty acid chain length

23
Q

What factors cause brittleness in suppositories?

A
  • synthetic fatty bases most brittle
  • can be induced by rapid cooling
  • reduced by Tweens (increase plasticity)
24
Q

Why is volume contraction important in making suppositories?

A
  • required to eject suppository

- undesirable at base of suppository (overfill)

25
Q

Why is rancidity important in making suppositories?

A
  • resistance of the fatty base to oxidation measured by quantity of peroxide
  • may require an antioxidant
26
Q

What appearance factors are important when making suppositories?

A
  • odour
  • colour
  • surface condition
  • shape
27
Q

What factors are used to check quality control in making suppositories?

A
  • appearance
  • weight
  • disintegration time
  • mechanical strength
  • content uniformity
  • drug release from suppositories
28
Q

What weight factors are important when making suppositories?

A

BP limits:

  • weigh 20 suppositories individually and together
  • no more than 2 > 5% deviation form average weight
  • none deviate > 10%
29
Q

How is disintegration time used to check for quality when making suppositories?

A
  • complies with BP disintegration test for suppositories and pessaries
  • does not relate to suppositories intended for modified release
30
Q

When is disintegration acheived?

A

When suppository is:

  • dissolved or
  • separated into component parts
  • softened (no solid core)
31
Q

What are the time limits for disintegration of a suppository?

A

Fatty base - no more than 30 mins
Water soluble base - no more than 60 mins

Pessaries - no more than 60 mins

32
Q

What is the temperature of the rectum?

A

Not necessarily 37C

- implications for drug release from suppositories

33
Q

What other local rectal formulations are available?

A
  • ointments/creams (e.g. haemorrhoids)

- enemas (aqueous or oily suspensions or solutions for evacuations /X-ray diagnosis)

34
Q

What other systemic rectal formulations are available?

A
  • tablets - do not disintegrate well in low volume of rectal fluid
  • capsules - soft shell, contents solid at room temperature. Similar release profile to suppositories - suitable for tropical climates. Special machinery required
  • micro-enemas - rapid bioavailability but costly and difficult to administer
  • retention enemas
  • large volume enemas

MPharm 2 - PH2107 (26 decks)

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