Well, Benadryl has a warning on it, but my though is maybe there is someting else that could work that doesn't cause drowsyness, just doesn't seem good to have your rescuee fall asleep and be dead weight.
Maybe its just me that gets affected, my wife seem to be affected similarly, whe's had a couple minor surgeries and the anastesia (hate trying from work with no spell checker) really knocks her out. My guess is because we've never had any kind of alcohol, tobacco, or any of the less than legal substances in our bodies we don't have any tolerance to any of those kind of chemicles.