Pharmacy IV Math

by Amy
(FL)

If 10mL of a nitroglycerin injection (containing 5mg per mL) was used to make 1L of IV fluid, what is the w/v% strength of nitro in the finished product?

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NTG percent problem
by: Brad Wojcik, Pharm D

You can either break this problem up into a couple of smaller problems or do it all in one step. The first step is always writing down the units of your answer. In this case it is a percent weight/volume, so the units of the answer will be % g/mL. (w=g, v=mL) The easiest way is to first calculate the amount of NTG in the 10 mL. 10 mL (5 mg/mL) = 50mg.
So, you are starting off with 50mg/1 L and you have to end up with the units of % g/mL. You have to change mg to g, L to mL and add the %. Changing the 1 L to mL, we are starting off with 50mg/1000 mL.
50 mg/1000 mL (1 g/ 1000 mg) (100%) = 0.005 % g/mL or 0.005% w/v. Remember, to add the %, just multiply by 100%. One step: 10 mL NTG soln/1 L (1 L/1000 mL) (5 mg NTG/ml NTG soln)(1 g/1000mg) (100%)= 0.005% g/mL or 0.005% w/v.

My answer
by: Anonymous

I got 0.05% w/v
Is that right? I don't know how you got 0.005% w/v.

Strength solution
by: Anonymous

%Strength = mg/mL x 100

10mL----> 5mg * 10 mL---> 50mg
1L---? 1000mL

% = 50/ 1000mL x 100


%S = 5%


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