Bit surprised at the level of hostility here.
Even more surprised that some think that there is no problem.
(usual aviation culture is that we have to positively prove safety).
Fact is, legislation has been passed in many countries mandating testing for drugs and alcohol (for a wide range of personnel in the UK - based on reasonable cause - i.e. if anyone "reliable" reports you). So its a fact, get used to it.
The legislation makes it an absolute offence to have drugs or alcohol in your body and sets specific limits for alcohol.
If you are tested positive, then you are guilty of a criminal offence and there is no defence (which is why a zero-tolerance level of 0.2% has been set). It seems unlikely that anyone found guilty would be returned to work......... and any airline that did not report "unfit" flight crew could be considered guilty of conspiracy - which reduces the scope for in-house rehabilitation.
What is of concern is that (zero tolerance) limits have been set for alcohol (.02%), but testing for "drugs" has been left undefined. "Drugs" includes illicit, prescribed and over the counter concoctions - anything that may impair your function - we just don't know what yet.
The body metabolises alcohol quickly, but is less efficient with other "drugs". If a zero tolerance level is set for "drugs" (as with alcohol) then an individual is likely to test positive several days after imbibing......... This could be a problem (whether for cocaine, ectasy or a prescribed anti-depressant).
What we need to know is what is meant by "drugs"?
Personally, I think random testing is just a prudent measure
and might encourage anyone with a problem to do something about it, before they lose their licence or their life.
And as long as we know what we are being tested for.........