magick-
Any professional aviator who meddles in any way with drugs, either hard or soft, is a complete fool. It's an absolute no-no. You may have noticed on another recentr thread that even the alcohol limits for pilots in UK have now been lowered and there have been a couple of well-publicised cases of pilots being arrested in other countries after testing positive for alcohol.
Many of us are also subject to random drug and alcohol abuse tests at least twice a year and these tests easily pick up the presence of drugs such as cocaine and opiates (even the codeine - an opiate derivative itself - in some over-the-counter cough suppressants will register a positive).
I don't know of any professional aviator who takes drugs, do you? If so, maybe you should refuse to fly with them or consider talking to them about getting help for it.
Drugs and flying mix about as well as clouds and mountains if you're flying IMC - stay well clear of both!