1. Drug calculation formula
Strength required volume of stock
Strength of hand X
= volume required
How many 50 mg tabs should be given for a dose of 75mg?
75 x
= 2 = 1 1/2

2. 200 Ordered: 15mg. Stock on hand 30mg. How many tablets? 15 x 1 = 1
Ordered 300mg. Stock is 200mg in one tab. How many tabs?
300 x 1 = 1 1/2
200

3. Steps: Convert 0.25mg to mcg 1mg = 1000mcg 0.25 mg = 250mcg
Patient is ordered 0.25mg of digoxin. The digoxin available is in tabs containing 125mcg. How many tabs should the patient receive?
Steps:
Convert 0.25mg to mcg
1mg = 1000mcg
0.25 mg = 250mcg
then apply formula:
250/ 125 x 1 tab = 2 tabs

4. A patient is ordered 150mg of aspirin. On hand are tablets of 300mg
A patient is ordered 150mg of aspirin. On hand are tablets of 300mg.How many tablets do I give?
150/300 x 1/1 = ½ tab.
The stock on hand of diazepam is 5 mg. How many tablets are to be administered if the order is for 12.5mg?
12.5/5 x 1/1 = 125/50 x 1/1 = 5/2 x 1/1 = 2.5 tabs

5. A syrup contains penicillin 125mg/5ml
A syrup contains penicillin 125mg/5ml. How much syrup do I administer for 250mg?
250/125 x 5/1 =
2/1 x 5/1 = 10/1 = 10 ml
480mg of Paracetamol is prescribed. The stock solution
is 120mg in 5ml. How many ml do I administer?
480/120 x 5/1 = 4/1 x 5/1 = 20/1 = 20 ml