Lessons · Pharmacy · a liquid dose in millilitres
A liquid dose in millilitres
Reduce the stock to milligrams in one millilitre, then divide the milligrams wanted by that.
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
Oral liquids are labelled as so many milligrams in so many millilitres, and the syringe in the bag is marked only in millilitres. Somebody has to turn one into the other, and it is you.
How to think about it
Two steps, always in the same order. First, milligrams per millilitre: the strength divided by the volume it is stated in. Second, the dose: milligrams wanted divided by milligrams per millilitre. Then check the size before you write it down.
Worked example
Stock: 250 mg / 5 mLTwo hundred and fifty milligrams in every five millilitres.
250 mg / 5 mL = 50 mg per mLReduce it to one millilitre first. Everything after this is easier.
Order 400 mg: 400 / 50 = 8 mLMilligrams wanted over milligrams per millilitre.
400 mg is more than 250 mg, so the answer had to be more than 5 mLAnd 8 mL is. That is the size check.
Your turn
The stock is 100 mg/mL and the order is for 350 mg. Write the volume of one dose.
350 / 100 = mL
Solve one, graded on the server
The trap
Using the 5 mL from the label as if it were the dose. It is the volume the strength is quoted over, not the amount anybody takes.