Help with Dosage Calculation

  1. I know the rules on calculating ml when reconstituting, but this is asking grams / mL and am not sure how to go about it. any input?

    Order: Zosyn 2.5g
    Available: 3.375g vial of powered Zosyn

    Directions: Reconstitute Zosyn w/ 5mL of saline for a total solution volume of 5mL

    The concentration is ____ g/mL
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  2. 12 Comments

  3. by   Rose_Queen
    What do you think is the first step you need to take? Think about what you are doing with the powdered drug.
  4. by   sebass19962014
    I figured I should determine the amount for the dose required in which I concluded to be 3.7 mL per dose. I get stuck there and am not sure how to determine the exact amount of powdered medication (grams) in each of the mL once reconstituted. Would it be asking the concentration per dose or per vial after reconstitution? If per dose, wouldn't it be the simple answer of 2.5g since its the dose I am looking for and am just over thinking it? Or per vial in which case I would just divide the 5mL by 3.375 and get 1.48?
  5. by   Wuzzie
    You're on the right track but are you sure it's 5ml divided by 3.375? When you did that you got 1.48 gm/ml. If you have a total of 5ml in the vial what would the total grams be? Is it more than what you started with? I think you already figured out the answer but don't realize that you did. How did you come up with the 3.7ml/dose which, BTW, is correct?
  6. by   sebass19962014
    If after reconstitution of the vial I get 5mL, would the vial still contain the initial 3.375 g of powdered med I put in?
    I initially did the cross multiplication:


    2.5g X 5mL --> 12.5/3.375g = 3.7mL
  7. by   Wuzzie
    I think you're getting it. Yes it would. You are reconstituting which just means turning something dry into something wet. In this case powder into liquid. The amount of medication does not change, just its form. So if you have 3.375 grams in 5 ml how many grams would be in 1 ml?
  8. by   sebass19962014
    Okay, I see where it's going. In 1ml it would give me 1.48 for the entire solution. When doing just the dose of 3.75 and dividing it by my ordered 2.5, it still gives me 1.48 regardless. So I did have the answer the entire time haha.
  9. by   Wuzzie
    Oops. Maybe I've confused you. If you have 1.48 grams/ ml then in a 5 ml vial you'd have 7.4grams per vial and that's not possible. You need to divide the grams by the volume. So you have a total volume of 5 ml that contains a total dose of 3.375 grams. Try that and see what you get.
  10. by   sebass19962014
    I'd do the opposite right? 3.375/5, which would give me 0.675. Haha I just misplaced my dosage. I'd do 3.375/5 x ml/1. Then cross multiply and get 0.675.
  11. by   Wuzzie
    Yay!!!! You got it. Does it make sense to you? Do you think you could do a similar problem on your own?
  12. by   sebass19962014
    Yess! Thank you so much, I feel fulfilled. I do believe I can tackle questions like these now. I tend to
    look at the question as a whole instead of just picking out necessary information and filtering out the extra that throws me off.
  13. by   Wuzzie
    You will find that nursing test questions, especially med math, are filled with what are called "distractors". This is information designed to confuse you. You are right when you say you need to pick out the necessary information and ignore the rest. Realizing this is about 90% of what you need to solve the equations. You will do fine.

    I also want to make mention to other nursing students. This exchange is a great example of why we don't just solve the problems for you. We are frequently called mean and rude when we ask you to show your work. But if I had just solved it for Sebass she may not have truly gotten the concept and would have struggled when faced with a similar problem. Because she was willing to do the work she now has a handle on the concept and feels a sense of accomplishment (you should Sebass!) which is a very good thing! We are delighted to help students who are willing to participate and take an active role in their education. Keep the questions coming.
  14. by   Mavrick
    A totally satisfying exchange of information.

    I'm very proud of you both. What a fine snack that was!!

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