dosage calculation problem

[GaNicuRN14]

I'm confused on this particular problem. Can someone please explain how you would solve this? Thank you!

250mg of Ceptaz must be prepared. The drug its available in a powdered drug containing 1g. Directions are to add 10mL solution to yield 90mg in 1mL. How many mL should you administer?

[nurseprnRN, BSN, RN]

Are you sure the question says 90mg per 1mL? If you dilute 1g with 10mL what do you get for a concentration?

There are a number of drugs that actually do that. It has to do with how the diluent molecules slide together (or don't) with the drug. I am embarrassed to say I can't explain it better.

However, OP, the answer to your question lies in the parts of the question that are factual (as presented, anyway). You are told that your final solution is 90mg/ml, and you have to give 250mg. That's all you need to know to do your arithmetic.

[nurseprnRN, BSN, RN]

Thank you! I got one more for you...

3/4 strength Osmolite must be prepared. Available is full strength. To prepare 175mL of feeding, how much Osmolite should be mixed with how much water?

No idea how to set that up :/

Let's think about this. Draw a beaker divided into fourths. Color in three-fourths. The total is 175cc. How much water is in it, if 3/4 of it is Osmolite? 1/4 of it is water, then, right?

[MandieeRN]

I think I figured it out I set up the ratio 90mg/1mL=250mg/xmL and got x=2.77, the answer key said 2.8[/quote']

These problems are meant to confuse you. One must use critical thinking. Also, expose yourself to dosage calculations a lot. I use to really struggle with these. They are way more simple when you look for what the question is really asking then try to solve. I always look at the end of the problem and decided what will be my final conversion and go from there. It's easier for me when I do this. Practice makes perfect.Good luck!

[tokebi]

There are a number of drugs that actually do that. It has to do with how the diluent molecules slide together (or don't) with the drug. I am embarrassed to say I can't explain it better.

However, OP, the answer to your question lies in the parts of the question that are factual (as presented, anyway). You are told that your final solution is 90mg/ml, and you have to give 250mg. That's all you need to know to do your arithmetic.

I agree, 90mg/ml is the final concentration given and that's all we need to calculate the problem.

As far as how we get that concentration when 10ml of diluent is added, I think we can assume that the solutes (drug powder) has significant volume even in solution. In this case, we have final volume of 11.11ml after adding 10ml. When making certain solutions in chemistry lab, you'd pour the diluent little by little until you reach the final volume you want. But we rarely do that when we mix drugs on the floor. Instead of mixing to a predefined concentration, we mix with a predefined volume of diluent and therefore, we'd always get a slightly larger volume that what we mixed with.

[nurseprnRN, BSN, RN]

I agree, 90mg/ml is the final concentration given and that's all we need to calculate the problem.

As far as how we get that concentration when 10ml of diluent is added, I think we can assume that the solutes (drug powder) has significant volume even in solution. In this case, we have final volume of 11.11ml after adding 10ml. When making certain solutions in chemistry lab, you'd pour the diluent little by little until you reach the final volume you want. But we rarely do that when we mix drugs on the floor. Instead of mixing to a predefined concentration, we mix with a predefined volume of diluent and therefore, we'd always get a slightly larger volume that what we mixed with.

:: dopeslaps own forehead:: Of course, that's it.