Section 3: Calculating the Size of a Single Dose
If you know the total amount of drug present and you know the number of doses needed, then you can calculate how big a single dose is.
150 ml of solution X is to last for 30 doses. What is the size of each dose?
If there are 150 ml of solution and this has to be divided into 30 doses,
then the size of a single dose is: 150 / 30ml
ie a single dose is 5 ml.
Total amount of drug = size of single dose x number of doses
which rearranges to:
Size of Single Dose = Total Amount
Number of Doses
Size of Single Dose = 150 ml
30
Size of Single Dose = 5 ml
15 doses of drug Y can be given from 3g of drug Y. What is the size of a single dose (in milligrams) ?
Convert the mass in grams to milligrams:
3g = 3000mg
If 3000 mg are to be divided into 15 doses, then
the size of a single dose is 3000 / 15 mg
The size of a single dose is 200 mg.
Total amount of drug = size of single dose x number of doses
which rearranges to:
Number of Doses
15
Size of Single Dose = 200 mg