International - How to control the rise of drugs under Legalisation?

[FuBai]

Methamphetamine is pretty much unheard of in Britain to the populace at large. Even within drug taking circles very little is known about the drug. Recent police reports say they have discovered evidence of use within every city, but this is mostly limited use and the availability of this drug is very small, confined to small bath tub chemistry productions due to the problems of getting large amounts of ephedrine and pseudo-ephedrine, the precursor chemicals needed to manufacture meth. So Britain's problem at the moment with this virulent drug is no where near that of the USA, where precursors are more available and the borders more open to Meth importation from South East Asia which has become a massive Methamphetamine producing region whilst Opium production there declines, as well as Mexico where further vast amounts are made.

We know Methamphetamine is addictive - some people claim to develop psychological addiction within 2 uses of the drug. This would be much less of a problem if the drug worked in the same way as nicotine, but it actually has a very strong and extended period of intoxication (12 hours), during that period it is incredibly hard to execute even simple procedures. In comparison to cocaine and opiate use, which, whilst lowering productivity in the work place, does not cease productivity altogether, it could be very damaging. Meth addicts, even under legalisation, would have a far more serious problem holding down a job than either Heroin or Cocaine addicts, due to the nature of the drug.

So we know Methamphetamine is a threat; a serious problem for America already and something most Britons would hope to avoid. Even browsing this website's Meth forum - a site composed of pro-legalisation drug users - very few people have anything nice to say about the drug. It would be hard to find a thread in any other forum entitled "It steals your soul and you don't even notice." So, my question is, under a legalised system how do we control and prevent Methamphetamine usage from becoming a major problem in the UK? And here's a more general question for everyone from every country - how do you stop and control the rise of any new drug that poses a serious threat to society under legalisation? I'm looking for some ideas before I lay out one of my theories.