Category: Compounding Corner (page 2 of 2)

February Compounding Corner Answers

Were you able to correctly answer the questions to the February Compounding Corner?

  1.   A solution is a liquid preparation that contains one or more active ingredients dissolved in a suitable vehicle. In contrast to a solution, a suspension is defined as a preparation where at least one of the active ingredients is suspended throughout the vehicle (not dissolved in the vehicle) and so the preparation will require shaking before a dose is administered.
  2.   Alcohol 90% v/v is used as the solvent of salicylic acid in this preparation.
  3.   This is an unofficial formula. We have to check that all the ingredients are within a safe dosage limit and are compatible.
  4.   1g of salicylic acid dissolves in 2.2 ml of alcohol 90% v/v 8g of salicylic acid dissolves in 2.2*8=17.6 ml *0.83=14.60g of alcohol 90% v/v
  5.   V=m/µ then 50g/0.89g/ml= around 56 mL so we will use a bottle of 60ml.
  6.   Salicylic and lactic acids are keratolytics. They work by breaking down the thick top layer of skin and increasing the amount of moisture in the skin. Salicylic acid causes the wart, corn, or callus to gradually peel off.
  7.   Flexible collodion works by forming a protective coating over the treated area. It helps to keep the area clean and also keeps the salicylic acid and moisture in contact with the skin.
  8.   Alcohol 90% v/v is a colorless liquid with a characteristic odor and taste.
  9.   An excipient is a substance formulated alongside the active ingredient of a medication. It is included for the purpose of long-term stabilization, bulking up solid formulations that contain potent active ingredients (e.g.: bulking agents, fillers, diluents), or to confer a therapeutic enhancement on the active ingredient in the final dosage form, such as facilitating drug absorption, reducing viscosity, or enhancing solubility. However, excipients are not intended to exert therapeutic effects at the intended dosage.
  10. The product name and list of the ingredients and their quantities,
    • Product-specific cautions : ‘For external use only’ will need to be added to the label as the product is a solution for external use ; ‘Keep out of the reach of children’ ; ‘Caution: Flammable and volatile solution’
    • Directions to patient: ‘Apply as directed’
    • Expiration date: It is suggested to apply a 4-week discard date as the solution contains ethanol.

February Compounding Corner

Compounding Corner – February 2017
Preparation of a Magistral Formulation

You receive a prescription in your pharmacy with the following details:

Patient’s name : Rose D
Age : 50
Sex: F

Prescription: External solution

Direction: Apply on the wart
Salicylic acid 8g
Lactic acid 8g
Alcohol 90% v/v qs dissolve
Collodion to 50g



1. What is the difference between a solution and a suspension?
2. What is the use of alcohol 90% v/v in this formulation?
3. You are asked to prepare this external solution. What should you check first?
4. How much alcohol 90% v/v (in grams) would be required to produce the 50g solution?
5. You have bottles of 30 ml, 60 ml, and 90 ml available in your pharmacy. Which size of bottle are you going to use and explain your choice?
6. Salicylic and lactic acids are active ingredients. What are their properties on the skin?
7. What is the use of collodion in this preparation?
8. Indicate two organoleptic properties of alcohol 90% v/v.
9. Alcohol is an excipient. Give the definition of an excipient.
10. What are the labelling considerations for this preparation?


Here are some indications to answer the questions:

– one gram of salicylic acid is dissolved in 2.2 mL of alcohol 90% v/v
– density of the solution: 0.89 g/ml
– density of alcohol 90% v/v: 0.83 g/ml
– note: density=mass/volume

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