# Who’s good with dosage calculations?? I need some help with a question please.



## ClarkKent (Aug 10, 2010)

I am in the middle of my class now and one of the question on a quiz read as followed (copied word for word from her quiz):

Doctor’s order: penicillin V potassium 1 tsp qid x 10 days
Available: 10-g bottle of penicillin V potassium oral suspension with the following instructions: Add 117 mL water to yield 20 mL oral solution.  Each teaspoon will contain how much?

250 mg
100mg
2.5mp
10mg

After taken this quiz and getting it wrong (2.5mg is what I guessed), I have asked a CNA, RN, and a Doc and they are telling me that something is missing, but when I ask the teacher, she is telling me that everything is there that I need and will not help me find the correct answer.  Can anyone show me how to answer this question so I can find he errors in my math?  No I can not retake this test so I am not cheating.  Thank you for you help!!!


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## 8jimi8 (Aug 10, 2010)

How does 117 mls added to the solution suddenly turn into only 20 mls?


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## AlphaButch (Aug 10, 2010)

If you mean a 200 mL solution, it can be done. Otherwise, none of the answers is correct.

10g in 200 mL using a standard 5mL teaspoon. Easy math. The part that people are saying you're missing is the teaspoon size most likely, as most folks don't know that off hand.


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## MasterIntubator (Aug 10, 2010)

I think you missed some "word for words' in this scenario. ( we can rule C out.. .as "mp" is not a unit ).  That leaves A, B and D.  
But with the correct internet filters in place, I think I can convert this stuff easily based on having done this stuff in pharm class:

You have 10 grams of Penn VK.  The package insert tells you to add 117 ML liquid to the powder, and in doing so... you will now have a new volume of 200 ML.  
Sooooo... in 200 ML you have 10 grams.  We break this down to the lowest ( and easiest ) number to work with.    ( 10,000 MG / 200ml = 50 MG/ML )

Sooooo... each ML is 50 MG.   A teaspoon is 5ml.  

5 ML x 50 MG = 250 MG.  <---- each teaspoon has this much in it


( I broke Grams down to MG, as it is easier for me, less confusion, and I drop the decimal.... in which decimals make me mad. )

"A" is the answer for the question.

:-/


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## ClarkKent (Aug 11, 2010)

MasterIntubator, thank you that makes a lot more since now that it is broken down like that.  Thank you to all for the the help.  That is the only question that I missed in the class and it really pissed me off


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