Compounding Corner – April 2017
You receive the following prescription in your pharmacy:
Patient: Jimmy R.
Prescription: 12 Glycerin suppositories using the following formula:
Glycerin Suppositories (105 g)
Glycerin 91 g
Sodium stearate 9 g
Purified water 5 g
Directions: Insert ONE suppository into the rectum when required.
- What is the use of this product?
- Explain the role of the components in this preparation.
- In compounding this prescription, you calculate for two extra suppositories to account for unavoidable loss in compounding. Calculations are therefore based on the amounts required to prepare 14 suppositories. What is the mass of glycerin-sodium stearate base that would be needed to prepare 14 child-size (2 g suppositories)?
- What size of suppository mold would you have used for an infant? For an adult?
- How many grams of sodium stearate are required to fill the prescription?
- What is the use of sodium stearate in this preparation?
- What is the volume of purified water required?
- What precautions should be taken when choosing the container of the suppositories?
- What are the labelling considerations for this preparation?
Indications for question 3: The glycerin-sodium stearate base has a density of 1.25. To correctly calculate the quantities required, the amount that would be required to fill the nominal weight will need to be multiplied by a factor of 1.25.
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- This product is used to treat constipation.
- Glycerin, a hygroscopic material, contributes to the laxative effect of the suppository by drawing water from the intestine and also from its irritant action on the mucous lining. The sodium stearate, a soap, is the solidifying agent in the suppository and may also contribute to the laxative action.
- A 1 g mold is usually used for an infant’s suppository, and a 4 g mold for an adult’s suppository.
- 14*2*1.25 = 35 g, total weight of mixture
- 91 (g)/105 (g) = x (g)/35 (g) ==> x= 30.3 g of glycerin
- 9 (g)/105 (g) = x (g)/35 (g) ==> x= 3 g of sodium stearate
- 5 (g)/105 (g) = x (g)/35 (g) ==> x= 1.7 g of purified water, which corresponds to 1.7 mL.
- The glycerin suppositories have the disadvantage of being very hygroscopic, therefore they must be protected from atmosphere and wrapped in waxed paper or tin foil. The suppositories could also be made in a disposable mold.
- The product name and list of the ingredients and their quantities.
The size of the suppositories (2 g) could be added as suppositories can be available in different sizes.
Product-specific cautions: ‘For rectal use only’ will need to be added to the label as the products are suppositories for rectal use; ‘Keep out of the reach of children’
Directions to patient:’ Insert ONE suppository into the rectum when required.’
Expiration date: 3 months.