A traditional ED practice has been to combine promethazine as an anxiolytic adjunct to morphine for patients with musculoskeletal pain (eg back pain).
However, when compared to morphine alone, this combination does not lead to greater analgesia or decrease anxiety. It does however prolong ED length of stay.
This use of this "pain cocktail" is not recommended
References
Behrbalk E, Halpern P, Boszczyk BM, et al. Anxiolytic medication as an adjunct to morphine analgesia for acute low back pain management in the emergency department: A prospective randomized trial. Spine (Phila Pa 1976). 2014;39(1):17-22.
