The study, by doctors at St Thomas' Hospital in London, identifies a series of common symptoms for Ecstasy users being admitted to hospital, known as Saturday night fever.

The BBC's James Westhead: Little is known about the drug

These include dizzy feelings, nausea, collapse or loss of consciousness, anxiety, palpitations and raised temperature.

The syndrome is known as Saturday night fever because the most common time for admissions is between 10pm on a Saturday and 9am on Sunday.

The identification of the symptoms could help hospitals to be more alert to the possibility of drugs being behind admissions.

Cocaine most abused

Most of the 48 consecutive cases of Ecstasy-based emergency admissions the researchers studied over a 15-month period were the result of drug-taking at nightclubs.

Many Ecstasy users also use other drugs

Half of those admitted had been using other drugs, mostly cocaine and amphetamines.

Dr Hugh Williams, one of the authors of the report published in the British Medical Journal, said polydrug use seemed to have become "the norm" for young adults.

Ecstasy users who took other drugs were more likely to have serious side-effects than those just taking Ecstasy because of the reaction between the different drugs.

These included delirium, seizures and, in one case, coma.

Previous use

The researchers also found that up to 40% of those admitted said they had taken Ecstasy before, the implication being that they had suffered no side-effects.

Dr Williams said: "Ecstasy is not quality controlled and people can have idiosyncratic reactions to any medicine.

"Just because they have used Ecstasy safely before does not mean they can continue to do so."

The average age of ecstasy users admitted to hospital was 22. Men were twice as likely to be admitted as women.

Dr Hugh Williams: Raves could exacerbate Ecstasy's side-effects

At least 56% had taken Ecstasy at a nightclub or rave, while 37% did not say where they took the drug.

Most had taken up to two tablets, while some had taken as many as eight on the night they were admitted to hospital.

Although the researchers said the numbers of those admitted to hospital over the 15-month period was low, they said this probably underestimated the problem.

They said many people experiencing side-effects did not seek hospital help.

Dr Williams said he believed the hot, crowded atmosphere at nightclubs and raves combined with non-stop dancing could exacerbate the effect of the drugs.

Education needed

He recommended that drug users admitted to hospital be referred to specialist drug agencies for advice, particularly those who had taken different types of drugs.

He also thought drugs education should be given to children from a young age.

He added that users who were determined to continue should minimise the harm they faced by taking breaks from dancing, drinking salty water, reducing the amount of drugs they took and avoiding taking different types of drugs which could react together.

Around 500,000 people are thought to take Ecstasy at weekends in the UK and up to 9% of young people are said to have tried the drug.