Lessons · Pharmacy · milliequivalents from milligrams
Milliequivalents from milligrams
Milliequivalents are milligrams divided by the equivalent weight, and the equivalent weight is always given to you by the problem.
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
Electrolytes are ordered in milliequivalents and stocked with a milligram strength on the label. The bridge between the two is one number that is written on the order or the reference in front of you, and never remembered.
How to think about it
Read the equivalent weight off the problem, in milligrams per milliequivalent. Then milligrams divided by it gives mEq, and mEq times it gives milligrams. Multiply back at the end; that is the check.
Worked example
mEq = mg / equivalent weight in mgOne division, once the equivalent weight is in front of you.
Equivalent weight given as 74.5 mg per mEqTaken from the problem, not from memory.
1,192 mg / 74.5 = 16 mEqThe division.
16 mEq x 74.5 = 1,192 mgBack the other way. If it does not return, the division went the wrong way.
Your turn
A salt has an equivalent weight of 50 mg per mEq. Write the milliequivalents in 600 mg.
600 / 50 = mEq
Solve one, graded on the server
The trap
Dividing the equivalent weight by the milligrams. It gives a small decimal that looks like a careful answer, and multiplying back does not return the milligrams.