dosage question

  1. 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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    About Lisa CCU RN

    Joined: Aug '05; Posts: 1,721; Likes: 160
    Registered Nurse
    Specialty: Geriatrics, Cardiac, ICU

    9 Comments

  3. by   GeminiTwinRN
    Is it 4.62 mls?
  4. by   Lisa CCU RN
    No.:spin: :spin:
  5. by   JentheRN05
    .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
    Last edit by JentheRN05 on Oct 31, '06
  6. by   Achoo!
    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?
  7. by   grace_device
    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...
  8. by   Daytonite
    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)
  9. by   crb613
    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
  10. by   JentheRN05
    Quote from Daytonite
    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.
  11. by   Lisa CCU RN
    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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