Lessons · Pharmacy · desired over have, times the quantity
Desired over have, times the quantity
The amount to give is what you want divided by what one unit holds, multiplied by the size of that unit: D / H x Q.
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
It is the one formula that covers a tablet, a capsule, a millilitre and a vial, and it is the formula on every technician exam. Learn it in one shape and it never changes shape again.
How to think about it
Label the three letters before anything else. D is the dose the order wants. H is the strength on the stock label. Q is the unit that strength comes in, one tablet or so many millilitres. Then divide, then multiply.
Worked example
D / H x QDesired over have, times the quantity that strength is stated in.
Order 500 mg, stock 250 mg tabletsD = 500 mg, H = 250 mg, Q = 1 tab.
500 / 250 x 1 = 2 tabsTwo tablets for one dose.
Order 100 mg, stock 25 mg tablets: 100 / 25 x 1 = 4 tabsThe same three lines, a different script.
Your turn
An order is for 40 mg and the stock is 20 mg tablets. Write the line that gives the tablets.
40 / x 1 = 2 tabs
Solve one, graded on the server
The trap
Putting the stock strength on top. H over D gives a number that looks sensible and is upside down, and the size check catches it: wanting more than one tablet holds must give more than one tablet.