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Pharmacy Dosage Simple Calculations- Please Need Help Now to learn

Discussion in 'Pharmacy' started by PrePharmStu2009, 07.12.11.

  1. PrePharmStu2009

    PrePharmStu2009

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    Pre-Pharmacy
    SDN 2+ Year Member

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    Questions
    1. What does D5 1/2 NS mean?

    I know that 5 % dextrose is 5 g/100 ml right? so 1/2 NS does that imply 77 meq/ 1000 ml NaCl concentration?

    What if it is 1/4 NS 500 ml...
    What is the concentration the of Na Cl then

    Questions
    2. Sodium Chloride comes in a concentration of 4 mEq/ml. How much NaCl must you add to sterile water to make the following solutions:

    1/4NS 250 ml NS 1000 ml , 1/2 NS 500 ml, 1/2 NS 1000 ml, 1/4 500 ml, NS 250 ml, NS 500 ml

    How do you do this problem? If someone can explain me the basic steps and show an example. How are concentrations based on volume. So for 1/4, 250 will concentration be 1/8 * (154) since 154 is normal and volume is reduced by 1/4 of 1000, so 1/4 NS???
    Last edited: 07.15.11
  2. type b pharmD

    type b pharmD

    Joined:
    02.24.09
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    Location:
    Pacific NW
    Status:
    Pharmacist
    SDN 5+ Year Member
    d5 1/2 NS = a solution containing 0.45% sodium chloride and 5% dextrose in sterile water.

    As for the making the bags. Just remember and think carefully about this .

    NS = 0.9% nacl = 154meq/L
    1/2NS = 0.45% nacl = 77meq/L
    1/4NS = 0.225% nacl = 38.5meq/L

    You dont need any more help than this. If you think hard and carefully about it, you will learn better and teach yourself new things.

    Calculating % to meqs conversions is annoying and for me takes like 10 minutes of reasoning through chemistry formulas and moles and milimoles. Most pharmacists I know recommend just memorizing meq's/L for some standard solutions.

    Oh, and btw: NS = normal saline. (0.9%, which is basically the same tonicity as the body's fluids.) 1/2NS is half of that, 1/4NS, 1/4, etc, etc, etc.
    Last edited: 07.12.11
  3. PharmDstudent

    PharmDstudent

    Joined:
    01.08.07
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    4,346
    Status:
    Pharmacist
    SDN 7+ Year Member
    Thanks! I had to use those today. :p

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