dosage question

Nursing Students General Students

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Specializes in Geriatrics, Cardiac, ICU.

Today I had a medicine that was 200 mcg powdered and it needed to be reconstituted in 5 mL of 0.9% saline. That makes 5mL of medicine with 40 mcg/mL. I get that because 40x 5= 200mcg. What I don't is this. I had to give 37 mcg of med. I did dimensional analysis and got

mL= 5mL 37 mcg= 0.925

200 mcg X

I know that is not right though. What am I leaving out? We had to call the pharmacy to get the dose, but to the RN's credit, she did know what it was off hand. I was the one confused and still am. I know the answer now, I wanna see if anyone can figure this out and explain it to me.

Please help.

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Specializes in ICU/PCU/Infusion.

Is it 4.62 mls?

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Specializes in Geriatrics, Cardiac, ICU.

No.

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Specializes in OB, ortho/neuro, home care, office.

.925ml has got to be it. Because if you think logically about this each ml has 40mcg of the med, so it has got to be just under 1ml. Gonna try another 'old school' way.

I still get .925ml both ways. No idea

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Specializes in Urgent Care.

If you add 5 ml of saline, your total volume will actually be more than 5 ml with the volume of the powder. Does it give the total volume with reconstitution?

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I often reconstitute meds that end up with different concentrations than you would think based on the amount of fluid you reconstituted with. So when you add 5mls fluid to the powder, somehow the total volume ends up at 4.2ml or something sneaky like that. That's they only thing I can think of...

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Specializes in med/surg, telemetry, IV therapy, mgmt.

Well, based on the information you've given, and working by dimensional analysis, I get the same answer you did.

37mcg
/
1
(dose desired)
X
5mL
/
200mcg
(dose on hand)
=
0.925mL
=
1mL
(rounded up)

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Specializes in Med Surg/Tele/ER.

I get 0.925ml working it two different ways.

dose ordered=37mcg

dose avail=200mcg/5ml

37mcg/200mcg=0.185mcgx5ml=0.925ml

Dimensional Analysis....mcg=37mcg/1x5ml/200mcg=185/200=0.925ml

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Specializes in OB, ortho/neuro, home care, office.
Well, based on the information you've given, and working by dimensional analysis, I get the same answer you did.

37mcg
/
1
(dose desired)
X
5mL
/
200mcg
(dose on hand)
=
0.925mL
=
1mL
(rounded up)

Yeah - I agree it needs to be rounded up - in this case with reconstitution and extra content.

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Specializes in Geriatrics, Cardiac, ICU.

Well, the pharmacy said it was 0.74 something, but my nurse told me to round up to 0.75 or 3/4 of a mL.

I still have no idea how they got this.

I know if I ever have to do this on my own, I'm checking with the pharm as my nurse did.

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