Drug advisers in Oxfordshire warned young people that dabbling with the designer substance mephedrone would be like playing “Russian roulette” with their lives.

The warning came as it emerged two teenagers in the county had collapsed and been treated by paramedics after taking the legal drug, which is also known as meow meow or MCAT.

A police spokesman said a 19-year-old man in Wantage needed medical help on Friday after taking a contaminated batch of the controversial stimulant.

The spokesman said a week earlier a 17-year-old girl in Witney collapsed after taking mephedrone at a house party.

Paramedics believed a reaction could have been caused by mixing the drug with alcohol.

In England and Scotland mephedrone has been linked to up to 25 deaths.

The director of Oxfordshire’s Drug and Alcohol Team (DAAT) Jo Melling warned about the effects of swallowing or snorting the white powder, which is sold as plant food on the Internet.

She said: “No one knows the long-term effects of this drug and it was not designed for human consumption. By taking any drug in combination with another drug, such as alcohol, you increase its risk by 100 per cent.

“The concern is even greater with mephedrone because we know even less about it and we don’t know what the chemical reactions are going to be.

“You also never know what this drug could be cut with. It could be cut with detergent or a more sinister drug. People who take it are playing Russian roulette with their lives.”

Home Office Minister David Hanson told the House of Commons he hoped an order outlawing mephedrone and making it a class B drug would come into force on April 16. The move was supported by Oxford West and Abingdon MP Dr Evan Harris.

Leigh Thompson, drugs co-ordinator for Thames Valley Police, said: “Although this substance is legal at the moment, it doesn’t mean it is safe.”