[fweimer]

As far as I understand it, crushing/injecting it makes it more likely to induce pronounced euphoria and other side effects that encourage abuse. But it was known from the start that it was addictive (causing a physical dependency) even if used as intended, simply because it is an opioid. Here's an older package insert:

https://www.accessdata.fda.gov/drugsatfda_docs/label/2009/02...

Among other things, it says “Physical dependence and tolerance are not unusual during chronic opioid therapy.” I'm no expert, but I think that explains why warnings about dependence weren't more pronounced. The drug was supposed to be distributed in a tightly controlled fashion due to these risks, after all.

In retrospect, the warnings at the start, and the information for patients read like recipes for abuse, though.