[maxerickson]

A single dose is unlikely to lead to physical dependence. Powerful opiates are often administered through an IV for things like oral surgery (my recollection of the sedation I had when I had my wisdom teeth out definitely includes euphoria in the moments before I fell asleep).

The issue is probably mostly that many of the people at a point where the first dose seems like a good idea are going to also think the second dose is a good idea.