# reconstitution drug problem

Posted
by blackout156 (New)

Hello everyone!

I've been up and racking my brain trying to solve this problem. and im almost getting dizzy. im really bummed out about this bc none of my answers make sense. I would like some help solving this problem please !!

Order: Erythromycin 750mg in 250 mL NS over 2 hours

Available: erythromycin 1g powdered vial, reconstitute with 20 mL sterile water for 50mg/mL

use a 15 gtt/mL set . Calculate your drops per minute (gtt/min)

ANY help is appreciated :)

Edited by blackout156

1,855 Posts

What have you tried doing? Where are you stuck?

4 Posts

I did this

750mg x 1ml/50mg= 15mL x 15gtt/mL = 225gtt

then divided 225gtt by 60min and that gives me 3.75 or 4gtt/min

im not sure if thats correct but it looks like it is

and also the 750mg in 250 mL NS and Erythromycin 1g available are numbers that are throwing me off and im not sure if they are supposed to be included somewhere in my equation

26 Posts

The formula is mL/hr X gtts/ml divided by 60 so it would be

(125)(15)/60

1875/60

31.25

31 gtts/min

I just finished my dosage calculations class and my professor was very strict about finding the hourly rate ALWAYS when doing these types of problems because that's what you have to put in the pump

Also they put a lot of extra info into these problems that isn't really relevant

Has 3 years experience. 150 Posts

(total volume to infuse x drip factor)/total minutes to infuse = gtt/min

Hint: You do need to do an additional calculation to get the total volume

4 Posts

750mg x 1mL/50mg = 15ml

then 15mL + 250 mL NS = 265mL

265mL x drip factor/total minutes to infuse

(265mL x 15gtt/mL)/ 120 min = 33.1

so, 33gtt/min

can anybody check if im correct?

Has 3 years experience. 150 Posts

you got it!

Specializes in 15 years in ICU, 22 years in PACU. Has 30 years experience. 1,578 Posts

Where are you getting the 250 NS? If it is a 250ml bag there is always a bit of overfill, so calculating the additional 15ml of reconstituted Erythromycin is really only necessary for school problems. In which case you would withdraw 15 ml of NS before adding the 15 ml of Erythromycin.

As if 33 vs 31 gtts/min is significant.

Specializes in 15 years in ICU, 22 years in PACU. Has 30 years experience. 1,578 Posts

The formula is mL/hr X gtts/ml divided by 60 so it would be

(125)(15)/60

1875/60

31.25

31 gtts/min

I just finished my dosage calculations class and my professor was very strict about finding the hourly rate ALWAYS when doing these types of problems because that's what you have to put in the pump

Also they put a lot of extra info into these problems that isn't really relevant

Exactly! In this case the Erythromycin calculation isn't even necessary. Just calculate how to run 250ml over 2 hours.