Suppository question answer

Question 1

Indicate the ideal properties of a suppository base (20 Marks)

Answer 1

• Melts at or just below body temperature (but solid at ambient temperatures) or dissolves in rectal fluid
• Non-toxic and non-irritating
• Therapeutically inert
• Compatible with all drugs, i.e. chemically inert
• Physically and chemically stable
• Easy to work with

(4 marks for each point) maximum 20 marks

Question 2

(b) Write concise notes on each of the following types of suppository base:
(i) Theobroma oil

Answer 2

Theobroma Oil (Cocoa butter) - glycerides of fatty acids
- Natural product , hence batch-to-batch variability
- Safe, non-toxic, non-irritating
- Melts at body temperature
- Polymorphic (four different forms; alpha, beta, beta prime and gamma with melting points of 22°C, 34-35°C, 28°C and 18°C, respectively. The
beta form is the most stable and is desired for suppositories. The lower melting point polymorphs eventually will convert to the more stable form over time.)
- Melting point depressed by the addition of liquids or soluble drugs (need to add a wax to raise melting point)

(2.5 marks for each point ) max 10 marks

Question 3

(b) Write concise notes on each of the following types of suppository base:
ii) Synthetic triglycerides

Answer 3

ii) Synthetic triglycerides
- Hydrogenated vegetable oils, e.g. Witepsol family
- range with different melting points and viscosities
- select the appropriate one for the drug used
- H15 for insoluble drugs, E75 for liquids/soluble drugs
- Safe, non-toxic, non-irritating
- Easy to work with
- can be reheated
- Little batch-to-batch variability

(2.5 marks for each point, maximum 10
marks)

Question 4

b) Write concise notes on each of the following types of suppository base:
iii) Glycerin-gelatin mixtures

Answer 4

Glycerin-gelatin mixtures
- Gel formed from gelatin, glycerin and water (14 %w/w gelatin, 70 %w/w
glycerin ,16 %w/w water)
- Gelatin content can be increased for a stiffer consistency
- Good for water-soluble drugs
- Glycerin is a laxative
- Gelatin type A = cationic and gelatin type B = anionic, therefore care with
charged drugs
- Water present, therefore preservative required
- glycerin = glycerol = (CH2OH-CHOH-CH2OH) trihydric alcohol

(2.5 marks for each point, maximum 10
marks)

Question 5

b) Write concise notes on each of the following types of suppository base:
(iv) Polyethylene glycol (PEG) HOCH2-(CH2CH2O)n-CH2OH

Answer 5

(iv) Polyethylene glycol (PEG) HOCH2-(CH2CH2O)n-CH2OH
- Low molecular weight (MW) PEGs (200 to 600) are liquid
- High MW PEGs (>1500) are solid
- Can mix MWs to give desired properties
- PEG acts as a cosolvent
- Will absorb water from the rectal mucosa, causing stinging. Therefore,
include water in the formulation (up to 20 %w/w)
- Water present, therefore preservativenrequired

(2.5 marks for each point, maximum 10 marks)

Question 6

c) You are asked to prepare and dispense 6 x 1 g suppositories, each
containing 150 mg of Bismuth Subnitrate BPC 1973. Allowing for a 50% excess
(i.e. calculating on the basis that a total of 9 suppositories will be prepared);
calculate the weight of each ingredient that will be required for correct
formulation of these suppositories. The displacement value of Bismuth
Subnitrate BPC 1973 is 5.0. Explain how the 1g suppository moulds can be
filled when the weights of the two ingredients do not add up to 9

Answer 6

Bismuth Subnitrate BPC 1973 has a DV of 5, ie 5 g of Bismuth Subnitrate
BPC 1973 displaces 1 g of suppository base
- Amount of base required = theoretical amount – displaced amount
= (9 x 1 g) – (amount of drug / DV of drug)
= (9 x 1 g) – (1.35 g / 5)
= 9 g – 0.27 g
= 8.73 g
- Final formulation is: Bismuth Subnitrate BPC 1973 1.35 g
Suppository base 8.73 g
 A displacement value (DV) of 5 means that 5 g of the drug will displace
1 g of suppository base
- This needs to be accounted for in the formulation, since suppository
moulds are filled by volume not weight.