The drug known as "meow meow" (mephedrone) bought on the internet varies in quality so much that users could be at risk of overdosing, according to new research by pharmaceutical scientists. Findings of the University of Sunderland study will be released at the inaugural Academy of Pharmaceutical Sciences Conference - UK PharmSci 2010 - The Science of Medicine, September 1-3. 

Six samples of the drug, which is now illegal, were bought over the Internet and tested. Although impurities levels were low, three samples revealed various particle size and crystalline form, which means that the drug is more likely to vary in its effect on and safety for the user. 

Lead researcher, Dr John Lough said "Mephedrone bought over the Internet does not come in the same crystalline form, there are different sizes. We tested six samples and identified three different types of crystals. 

"While our batches were almost free from organic impurities, the tests are a very good illustration that drugs of abuse are more likely to be of variable quality and therefore of variable safety and efficacy." 

Popular with young clubbers, the drug has been associated with a number of hospitalisations in the UK and cited as a possible cause of death.