Pain after surgery

This is the one place it has been properly measured in people. Across 150 patients after planned surgery, 20 micrograms placed into the spinal fluid gave profound relief lasting about 43 hours, longer than 500 micrograms of intrathecal morphine managed at 34 hours, and far longer than an injection into muscle at 11 hours. Patients also left hospital sooner than the group who had the injection into muscle. The amount is tiny because it is placed exactly where it works.