One man is critically ill and five others are in hospital after taking a hallucinogenic drug believed to be 2CB, described as a cross between ecstasy and LSD.
Police and paramedics were called to a house in Jesmond, Newcastle, at 3am on Friday after receiving a report expressing concerns for the welfare of six men, believed to be between 19 and 22, some of them thought to be students.
Police believe they took 2CB, which also known as bromo and nexus, an illegal synthetic drug which was bought over the internet.
Chief Superintendent Gary Calvert of Northumbria police said: "We were called to the address early this morning and six people have been taken to hospital, one is in a critical condition."
2CB is an illegal class A drug and is particularly dangerous when mixed with other substances. It often comes in purple capsules, but can be sold as white powder or as small pills. It is usually swallowed but can be snorted, though the latter is said to be extremely painful.
It is often taken in combination with other rave drugs such as ecstasy. At low doses the effects are said to be similar to those of ecstasy. At higher doses the effects are more like those of LSD.
Doses higher than 40 milligrams have been reported to bring on extremely frightening hallucinations, with users suffering terrifying panic attacks. Other possible side effects are anxiety, poor co-ordination, shaking and dangerously increased blood pressure and heart rate. The drug can also cause feelings of anger and distress, psychotic syndromes and depersonalisation.
Calvert said: "Anyone who may have taken the drug and feels unwell should seek medical attention immediately."