Lessons · Pharmacy · a dose written in milligrams per kilogram
A dose written in milligrams per kilogram
A mg/kg order is a multiplication: the milligrams per kilogram the order gives, times the weight in kilograms.
Hone is a place to practise a career, one idea a day. This is one of its lessons, written out in full and free to read without an account.
What it is for
Weight-based orders are how anything is written for a patient whose size matters, and the arithmetic is trivial. What is not trivial is that the weight arrives in pounds, and the multiplication does not care whether you converted it.
How to think about it
Kilograms first, from the chart. Then read whether the order gives milligrams per kilogram PER DOSE or PER DAY, because they are different numbers and the order always says which. Multiply, and label the answer with which one it is.
Worked example
Dose = mg/kg x weight in kgThe order gives the mg/kg; the chart gives the kilograms.
10 mg/kg x 25 kg = 250 mgOne dose, if the order says per dose.
110 lb / 2.2 = 50 kgPounds convert before anything is multiplied.
5 mg/kg x 50 kg = 250 mg per dose; tid = 750 mg a dayPer dose and per day are two answers; say which one you have written.
Your turn
An order gives 15 mg/kg per dose for a patient of 4 kg. Write the dose.
15 x 4 = mg
Solve one, graded on the server
The trap
Multiplying by the pounds. The number comes out 2.2 times too big and there is nothing in the answer to say so; only the unit on the weight catches it.