Question

1. Case:  A prescription for calls for compounding 60 mL of an oral solution for patient A.  This oral solution contains 45 mg of salicylic acid. The pharmacist decides to weigh this on a balance with a minimum weighable quantity of 120 mg and dissolve it an appropriate solvent to prepare the solution. Answer the following questions to explain how you will use the liquid measurement aliquot method to obtain the correct amount of salicylic acid to prepare this solution. When making this preparation, you want to minimize the amount of salicylic acid that is wasted.  The prescription is as follows:

Rx  Salicylic acid                            45 mg

      Cherry flavor solution             5 mL

      Ora-Syrupee                qs        60 mL

1. What is the target amount of salicylic acid for the liquid aliquot that will be used to make the 60 mL oral solution?

2. What is the maximum volume of the liquid aliquot can be used to make this preparation?

3. If you weigh 120 mg of salicylic acid on your balance and want to use an aliquot volume of 15 mL, how much solvent will you use to dissolve the 120 mg of salicylic acid.

Hint (helpful proportion):

Answer 1

Step 1: Weigh out a measurable multiple of the desired quantity

Compound requires 45 mg of drug

The minimum amount that can be accurately weighed out = 120mg

I will choose 3 to be the multiple factor , so 3* 45 =135 mg

Step 2 :Dilution

120 mg is the smallest amount of drug we can weigh out

120 * 3 =360mg of mixture desired.

360 mixture -135mg active drug =225mg diluent

Step 3 :Weigh the aliquor portion of diluant

used a multiple factor of 3

225mg total / 3= 75mg

therefore 75 mg of aliquot contains my 45 mg salicyclic drug