I had a patient who had D5 1/2 NS running and an order of flagyl piggybacked. I looked to see if the two were compatible in our drug reference page and I didn't see anything regarding the fluids so I called pharmacy. Pharmacy said they weren't aware of any compatibility so they told me to play it safe and run the abx via primary line and to temporarly stop the fluids. I passed this on to the next shift and the nurse told me that since Flagyl is compatible with NS and D5W then its compatible with D5 1/2NS even though it doesn't come out and say it in the reference manual. This doesn't really seem like a legit assumption to me (Idk tho, I'm still new!). I looked into it further and the pH of the fluids and stuff like that is all different. I was just wondering if this would be okay to do moving forward.