Not necessarily. After all, this particular drug is an opiate, derived from codeine.
Odds are, the users may not feel much pain, as the narcotic they’re taking is a painkiller. Horrifically ironic.
Good point, at the beginning anyway.
However, with so many nerve endings being exposed, I’m not sure if there are enough pain killers in the world that you could give somebody if they are that far into an addiction that they can literally rot away and not feel anything.