Our poison center and local toxicologists not only recommend 4-6 hours, but they distribute this information to us so we're aware of it, so I do it. They generally leave within 1-2 hours, and I don't hear about it until 10 minutes after they walk out.
Well, virtually any EM text is going to recommend 4-6 hours of observation (Same as most poison centers if you happened to call them for an opiod overdose though most of us never do). Personally, for the ones that are significant opiod overdoses....I've been watching them 2 hours. That has always made sense to me given narcan half life combined with potential for extended release narcotic ingestions, co-ingestions that they might not be reporting, etc.. Anecdotally though, there are a few I've discharged after an hour and I've always felt that with a reassuring exam, their risk was very low for any sort of adverse effect barring that they did not go back out and overdose again. Until now, all we've had is the St. Paul derivation study from 2000. Now we have a validation study and in my opinion, more of a leg to stand on if we discharge patients after an hour of observation. With all the practice patterns I've observed over the years, I'd say 1 hour obs is hyper aggressive for most EM docs. What I usually run into is that I recommend 2 hour obs and they virtually never stick around. Most sign out AMA.
For myself, 1 hour obs is a little aggressive for my historical comfort level, but I think the data is decent and seems to indicate that most traditional guidelines are probably overly conservative.