Mephedrone is a synthetic chemical (4-methylmethcathinone) that has become popular as a legal alternative to ecstasy. It is not presently covered by the Misuse of Drugs Act.

It was created as a 'designer drug', a substance chemically similar to illegal drugs, with similar effects on the user, but different enough to ensure it is not covered by present legislation.

Users describe its effects as similar to cocaine and ecstasy, with feelings or euphoria, alertness and empathy. Drug dealers have been known to sell mephedrone as ecstasy or cocaine, or cut these more expensive drugs with mephedrone. It is so popular among drug users, and its sale is so lucrative, that it is thought that many dealers are now supplying it as well as illegal substances.

The drug comes in a number of forms, most commonly as a powder or crystals, but also as tablets or as a liquid and is known by a number of names, including bubbles, meow, and M-CAT.

It is believed that the majority of mephedrone is manufactured in China, and imported to the UK directly. Such transactions are legal, and even after paying the cost of importation it remains very lucrative to buy several kilos of the substance, then sell it by the gram.

It has quickly become one of the most popular drugs among clubbers, this popularity comes from its current legality, and ready availability online.

However, the fact that the drug is not a controlled substance does not mean that it is harmless.

The possible side effects can include nose bleeds, joint pains, paranoia, heart palpitations, insomnia and memory problems. 

As it has only been around for a comparatively short period of time, there has been little work on its long-term effects.

One medical journal noted that use could lead to cardiovascular issues similar to those associated with cocaine or amphetamine use, as well as serotonin syndrome, a potentially life-threatening adverse reaction that can be linked to long term use of ecstasy or LSD.

Mephedrone has been particularly popular in Dundee, where a number of non-fatal overdoses have occurred.

It is currently banned in a number of countries, including Australia, Denmark, Sweden, Germany and Israel.

It is also illegal to sell it for human consumption in the UK, which explains why most of those who sell the substance market it as 'plant food.'