Lessons · Pharmacy · checking the answer by size
Check the answer by size before you write it
Before a number goes on a label, ask whether it should have come out bigger or smaller than the stock, and whether it is an amount a person could actually take.
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
Calculators do exactly what they are told, including a division done upside down. The size check is the thirty seconds that catches it, and it is the habit that separates a technician who has made one bad fill from one who has not.
How to think about it
Two questions. Is the dose bigger or smaller than what the stock volume holds, and does my answer agree? And could a person swallow, draw up or inject this amount? A number that fails either question goes back to the arithmetic, not onto the label.
Worked example
Order 125 mg from stock of 250 mg / 5 mLHalf of what 5 mL holds is wanted, so the answer must be under 5 mL.
250 / 5 = 50 mg/mL, then 125 / 50 = 2.5 mLUnder 5 mL. It passes the size check.
If it had come out at 10 mL, the division was upside downTwice the stock volume for half the dose is impossible.
An oral syringe holds 10 mL; a single oral dose of 40 mL is a stop-and-checkA number nobody could give is a number to work again.
Your turn
Stock is 200 mg / 5 mL, which is 40 mg/mL, and the order is for 60 mg. Write the volume, then see that it is under 5 mL.
60 / 40 = mL
Solve one, graded on the server
The trap
Trusting the screen because the arithmetic felt easy. The easy ones are where the upside-down division hides, because nothing about the number looks strange.