Med calculation question

locolorenzo22, BSN, RN · Jan 16, 2012

Okay, so what are they asking? how many militers to give the patient? okay, dose desired divided by dose on hand then times it by the solution available. 500mg/2000mg, the concentration should have been given. with 2mls of solution, then yes 1mls is the answer.

nurseprnRN, BSN, RN · Jan 18, 2012

i am reading this that you have 2000mg of drug in 100cc and you have to give 500mg, so that is 1/4 of 2000mg, so you need to give 1/4 of 100 cc, which is 25cc, not 0.25cc. at 60gtts/cc, that's 25gtts/min = 25cc/hr to give it over one hour. (hint: for a 60gtt/cc set, # gtts/minute = # cc/hr)

500/2000 x 100cc

=

1/4 x 100cc

=

25cc

where did you get that the answer was 1cc? did you figure that, or was that the answer given to you in the answer key? i have no idea whatsoever how that would happen or what locolorenzo is saying.

tlc2u · Jan 19, 2012

I can't figure out how to get the answer for this question, but I'll show you how I set it up.
Order: cefepime hydrochloride 500 mg IV, q12h
Avail: 2 g cefepime hydrochloride
instruction 60gtt/mL; 100 mL of D5W
It does not give a dilution amount, nor does it indicate how many mg/mL.
the equation I came up with was 500/2000 x ?mL = mL that patient should get. Is 2 g/ml implied if it is not listed on the label? If so that only gets me .25 mL. It does give an example of it being diluted to 3 or 4 mL, but even if I plug in those numbers I don't the right answer.
The question is how many mL of drug solution the pt should receive? and the answer is 1 mL.
They don't ask me to figure out gtt/min so I am assuming there is a clue somewhere in that info.
What am I missing here? I feel like the question is invalid.
Thanks!

The drug you are working with is an antibiotic and can come as a small vial of powder that you add 3 or 4 mL of liquid to or a large (100 mL) 1g or 2g piggyback bottle.

If a small vial of 2g cefepime is constituted with 4mL of liquid

and your order is for 500mg cefepime

Then:

4mL = 2g cefepime

AND

1mL = 500mg cefepime

This would give your answer of 1 mL.

When doing pharmacology math try to look at the question in relation to the medication in the question, how it comes and how you would actually prepare it in the real situation. for me this helps make sense of the question as opposed to looking at it as just another math question.

Good Luck.

nurseprnRN, BSN, RN · Jan 19, 2012

the question as the op gives it to us mentions the 100cc bag; this could mean that it doesn't matter at all how much drug there is in the bag, they just want to know how fast to run an iv to give 100cc/hr. in that case the answer is "100cc/hr," or 100gtt/min c the iv set specified.

imho, it is not reasonable for faculty to assume that a student would know that this med usually comes in a vial that is usually reconstituted c a given amount; however, most of the time, when you add xcc of diluent to a vial of powder, you do not get xcc of final volume, you get something like (x+y)cc. in this case you might get 4.6cc total, or 5cc, or something else entirely. it would be very important to measure the final volume obtained before (in this case) dividing by four to obtain the volume for your desired dose.

it is perfectly possible that the op omitted some critical part of the question, or whoever wrote the question did. the fact that we are having this discussion at this point suggests one of those two must have occurred.

all we know is that the op tried to figure it out with an equation that was inappropriate given the information at hand, and came up with a wrong answer trying to shoehorn her data into it. instructive, but not useful otherwise. now i think she can see what to do next. op, are you there?