I would 'accidentally' drop it down the drain or spill it or something. 'Oh damn sorry, so clumsy, didn't mean to do that, you didn't need it did you??' Calling the Police as standard would stop people who have od'd calling you in case you get the police involved. I'm a PCSO and I've always found that when I find someone who's od'd (quite often...) they will only get in the ambulance if they know I'm not getting involved (if they're concious that is). I think the ambulance service need to be neutral in this kind of situation in order to make sure people feel safe calling for help - even if it is their fault they're in that situation. That's my penny's worth anyway, for what it's worth!