1.Easy
Practice exercise (made-up values, not clinical guidance). A solution of benzalkonium chloride has a ratio strength of 1:2 000. How many milligrams m are in 50 mL?
1:2 00050 mL
m = mg
Pharmacy calculations worksheet with answers
2.Easy
A solution is 2% w/v. You need 36 mg of the drug. Draw up the volume in the syringe: what volume V is that?
2% w/v36 mg
V = mL
3.Medium
A solution has a ratio strength of 1:1000. You need 0.27 mg. Draw up the volume in the 1 mL syringe: what volume V is that?
1:10000.27 mg
V = mL
4.Medium
Practice exercise (made-up values, not clinical guidance). A vial contains oxacillin 2000 mg as a powder. The practice label says to add 11.5 mL of sterile water; the powder adds 1 mL to the volume. What is the concentration C in mg/mL after reconstitution?
2000 mg11.5 mL+1 mL
C = mg/mL
5.Hard
A vial holds 2000 mg of powder. You add 4.4 mL of diluent, and the powder adds 0.6 mL of volume. The prescription is 1880 mg. Draw up the dose: what volume V do you give?
2000 mg4.4 mL + 0.6 mL1880 mg
V = mL
6.Hard
Practice exercise (made-up values, not clinical guidance). You have 100 g of 2.5% hydrocortisone ointment. How many grams m of 0.5% hydrocortisone ointment must you add to make a 1.5% ointment? Round to the nearest whole gram.
100 g · 2.5%0.5%1.5%
m = g
Answer key
- 1. m = 25 mg
- 2. V = 1.8 mL
- 3. V = 0.27 mL
- 4. C = 160 mg/mL
- 5. V = 4.7 mL
- 6. m = 100 g
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