FYI information:
I just listened to a recorded webinar by Cahaba yesterday that stated, identical procedures will be denied if billed on 2 lines with the 2nd procedure applied with a modifier 59. They want these types (96372) procedures billed on one line only with 2 units (or more if documented) and not use the modifier 59. They are considering the 2nd line item to be a duplicate and will automatically deny.

If the documentation specifies two separate IM injections, you should bill with 2 units.
Do not assume that the drug(s) are mixed unless they state, query and find out for sure before sending a claim.