What you will notice

Within the hour of a spinal placement: pain falls away, deeply, and that is the effect the human record describes as profound. First day or two: relief holds from a single placement for around 43 hours, which is the longest measured figure in its record and the reason it was interesting at all. Across days and weeks of repeated exposure: tolerance begins to build as it does with any mu agonist, more slowly than with morphine, and so does physical dependence. Longer: these are the familiar costs of the opioid system itself rather than of this molecule, which is why its use has always been short, placed and supervised. Breathing is the thing watched most closely throughout, because that is what a potent mu agonist slows.