This from The Observer (article link):
Legal chemicals sold to fuel heroin profits
Jamie Doward Sunday September 7 2008
Organised criminal gangs are developing a lucrative trade in importing mass quantities of legal chemicals and selling them on to drug dealers to be used as cutting agents for heroin and cocaine.
The so-called 'smash' or 'bash' industry is now generating such large profits that some criminal gangs have stopped selling illegal drugs to focus on buying and selling legal chemicals, according to Drugscope, the charity that monitors the price of drugs on Britain's streets.
Legal chemicals imported from such countries as China and mixed with pure cocaine and heroin include the anaesthetics benzocaine, lignocaine and phenacetin. Other substances used include caffeine and tetramisole, which is given to pets to expel tape worms.
One person involved in the industry told Druglink, Drugscope's magazine: 'Dealing in smash is more attractive than dealing in illegal drugs because it's more profitable and it's not a class A drug. I know people who make a living out of selling this stuff.' Recent analysis by Drugscope has found the purity levels of cocaine are plunging, suggesting a growing demand for cutting agents.