Holland & Barrett has alerted staff to this trend among drug takers who mistakenly believe that 5-HTP, a herbal remedy for depression, can prevent the brain damage associated with frequent Ecstacy use.
Scientists say that if 5-HTP is mixed with anti-depressants such as Prozac or even alcohol it can cause excessive sweating, muscle cramps, and in extreme cases death.
Anti-drugs campaigners are also worried that people will be encouraged to believe that there is a "safe" way to take Ecstasy, which has caused more than 30 deaths in the past five years.
The natural herbal tablets, which have become the latest craze on the club scene, are sold in health-food shops and are being promoted by drug users on websites.
Although 5-HTP is the most popular of the herbal remedies, St John's Wort is also used by clubbers convinced that it will protect them.
The attraction of 5-HTP is its ability to boost the levels in the body of serotonin, a brain chemical that induces happiness and is depleted by long-term Ecstasy use. A study by scientists at Edinburgh University showed that people who use large amounts of Ecstasy suffer memory loss because the drug damages serotonin nerve endings in the brain.
In club circles, substances such as 5-HTP are known as "preloaders" in the belief that they prevent the low experienced after taking Ecstasy as well as other more serious side-effects. This belief is the major reason that "E" has regained its popularity.
Tom Whitwell, features editor of Mixmag, says that natural anti-depressants are part of the preloading culture. "This ranges from drinking water or grapefruit juice to taking tablets such as 5-HTP," he said. "It's becoming a habit with the more experienced Ecstasy users in this country.
"It's all about making drug-taking safer by boosting your serotonin levels and cushioning the `comedown'. But the claim that it prevents long-term brain damage is pretty shady."
Dr Janusz Knepil, a biochemist in charge of drugs toxicology at Gartnavel Hospital, Glasgow, says it is dangerous for people to regard 5-HTP as an antidote.
"The problem with `E' is that it can be made up of all sorts of bits and pieces and you don't know what you are getting," he said. "If 5-HTP breaks down the wrong way it can become a toxin itself. There is only one message and that is there is no safe way to misuse drugs."