IV Flow rate calculation...Please Help

[Samm06, BSN, RN]

Here is the question:

order: cimetidine 300 mg IV push stat

supply: cimetidine 300 mg per 2 mL

package insert instruction: For direct IV injection, dilute 300 mg in 0.9% NaCl to a total volume of 20 mL. Inject over at least 2 minutes.

Prepare ____ mL cimetidine.

Dilute with ____ mL 0.9 % NaCl for a total of 20 mL of solution.

Administer ____ mL/min or ____ mL per 15 sec.

I am having trouble with the second and third part of this question. I already got "prepare 2mL of cimetidine."

However, I don't understand how the book got 18mL for the dilute and 10 mL/min or 2.5 mL per 15 sec.

Do you get 18 mL because if you do 20 mL of total volume - 2 mL prepared of cimetidine?

Just need help setting up the problem the find mL/min

PLEASE HELP ME.

[203bravo, MSN, APRN]

It is supplied in 2 mL and you want to dilute it until you have 20 mL thus 20 mL - 2 mL = 18 mL

If you are going to administer 20 mL over 2 minutes = 20 mL/2min = 10 mL/min

15 sec is 1/4th of a min = 10/4 = 2.5 mL every 15 sec

this is all very basic math.

[Samm06, BSN, RN]

dang, i can't believe i couldn't figure that out. I think the wording of the question just messed me up when it said total volume of 20mL. didn't realize that would be the actual total amount i'm administering. But i guess i wasn't thinking right. Thank you.