How much to dilute an IV push med

I'm wondering how you would go about figuring this out. If a med comes in an ampule with a concentration of 400 mcg/mL, and the medication must be diluted to 50 mcg/mL, how much NS would you add? Say the ordered dose is 100 mcg, so its 0.25 mL as a dose. what would you add to the syringe to make it the correct dilution?
The drug insert sheet should tell you what to dilute with, how much to dilute with and what concentration per ml you will end up with... then you can do your med math per your MD ordered dose.

400mcg/xml = 50mcg/1mLWorking the algebra you get 8mL - the 1ml you already have means you'd add 7mL of whatever solution your drug guide says is appropriate.Then you work the math out againOrdered Dose � What you have on hand * The Route = How much to give100mcg � 400mcg * 8mL = 2mL