Mephedrone is also known as "bubbles" or "meow meow"
Police have issued a warning about the use of "legal highs" following the death of a woman in Dunfermline, Fife.
The 49-year-old is thought to have died after taking mephedrone, also known as "bubbles" or "meow meow". The substance is often advertised as plant food.
A number of people also became ill in Methil after taking the substance known locally as "white magic".
Police said legal highs such as solvents and plant food were dangerous because their effects were unknown.
The ambulance service was called to a house in Dunfermline on Saturday where a woman had collapsed after ingesting mephedrone.
She died a short time later in the town's Queen Margaret Hospital.
In the Methil incident, one woman was taken to hospital as a precaution.
Risk of death
Ch Supt Alistair McKeen of Fife Police said: "Potential users of 'legal highs' need to be aware of the dangers associated with these substances, a number of which have industrial uses as solvents or even plant foods.
"There is very little scientific evidence about these substances and the effects are often unpredictable.
"Combining legal highs with other substances such as alcohol increases the risks and there is a very real risk of death."
He advised people not to rely on the experience of users or sellers, and said the only sure way of being safe was not to experiment with these chemicals.
It is not illegal to buy mephedrone, although it is intended for use in plant food, not for human consumption.
But the Advisory Council on the Misuse of Drugs is reviewing mephedrone as a priority and is expected to decide later this year whether or not the law should be changed.
Mephedrone is already illegal in Sweden, Denmark, Finland and Israel, and is a controlled drug in Germany.