The small blue pill has is also known to make users feel energised before becoming highly aggressive.
The warning comes from the Royal Borough's Drug and Alcohol Action Team (DAAT), which said police haven't been able to identify what substances the drug is made from, which could be illegal or a 'legal high'.
The DAAT said after taking the pill, users are alert and awake before quickly becoming agitated, paranoid, confused and aggressive.
One young person was taken to hospital after taking the drug with cannabis.
Cllr David Coppinger, cabinet member for adult services and health, said: "Just because a drug is legal to possess doesn't mean it's safe.
"Young people should assume that if a 'legal high' produces similar effects to ecstasy or cocaine, then it is likely to have similar risks.
"Little or no research has gone into the effects of 'legal highs' and taking them with alcohol or other drugs just increases the danger."
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