If mice in the laboratory have tried it, it is more than likely that desperate athletes, keen for an edge on their competitors, will be trying it, too. That is the advice from one of the world's leading sports drug scientists, Dr Robin Parisotto. "With some of these things the technology is so new, the concept so bizarre, that there would only be a handful of well tapped-in athletes using them, but they will be experimenting at the Beijing Olympics because they are the ultimate," he said.

Viagra, a legal drug, opens up the blood vessels, allowing the transfer of oxygen to be increased. Athletes use it to help their performance - not in the bedroom but on the sports field. So too does inhaling the dentists' favourite, laughing gas. If the two are combined, some athletes think the effect is a double hit.

Researchers at the German Cancer Research Centre in Heidelberg showed this year that delivering DNA vaccines by tattooing was 16 times more effective than injecting intramuscularly or intravenously.

Apparently the vibrating tattoo needle primes the body's immune system and enhances the body's response to it. "The problem is that some of the drugs would now fly under the radar with the tattoo technique because athletes would be taking a much smaller dose - it depends on the drug and how sensitive the analysers are," Dr Parisotto said.

Still being researched, but already being experimented on by athletes, are emotoceuticals - drugs such as Neurodex which affect emotions. "These mind-clearing drugs have the ability to alter the emotions, for instance sadness and shyness, and so athletes would be very attracted to [them]."

World Anti-Doping Agency drug testers have already improved their ability to detect the third generation of EPO after drug manufacturers informed them of the chemical structure of an EPO variant, Cera. Tour de France cyclist Ricardo Ricco was the most high profile scalp, and his positive tests will have scared off others.

But Dr Parisotto believes the extensive publicity surrounding Cera will push the athletes to the next EPO variant, Hematide, or other artificial blood and plasma expanders and oxygen carrier products. Hematide is undergoing trials on human kidney patients in the United States.

"Cera is out of the bag, so the next EPO version off the production line is Hematide and with this drug patients take it every four to five weeks, not every second day."

Then there is the "exercise pill" - a drug containing DNA isolated for endurance and fat metabolism. Drug testers have been predicting gene manipulation for nearly a decade.

In studies mice fed the exercise pill showed improvements in running time of 44 per cent and more than 70 per cent.

Professor Ronald Evans, of the Salk Institute in California, said: "We were blown away. This is a drug that is like pharmacological exercise. After four weeks of receiving the drug, the mice were behaving as if they'd been exercised."

Other substances not yet on the banned list but popular among athletes are breast milk and cobalt.