Going up and down

Amounts in this molecule's world are micrograms into the spinal space, and the figure that matters is how much smaller it is than the alternative: 20 micrograms against 500 of morphine for a longer effect. Adjustment is a specialist judgement made with breathing and consciousness monitored, because potency this high leaves little room between relief and respiratory depression. The direction that gains most is better placement, not a larger amount. Into a vein, the amounts required are vastly larger for the same receptor effect, which is why that route stayed in the laboratory.