A young runner who collapsed and died during the London marathon had "significant" levels of a banned amphetamine-like fatburning supplement in her system, an inquest has heard.
Claire Squires, 30, suffered a cardiac arrest outside Buckingham Palace, where she was treated in a medical tent before being rushed to hospital.
Sanjay Sharma, medical director of the marathon and professor of cardiology at St George's Hospital, said the drug, DMAA, may have contributed to the excessive level of blood coming from her lungs, which was "unusual" in such a young person.
The inquest heard that the drug is not illegal although may be banned in competitive sport. She had planned to put a spoonful of it in her water bottle in case she 'hit a wall'.
Prof Sharma said the high potassium levels detected, her very stiff body and evidence of blood clotting, would "certainly fit with pure amphetamine use".
DMAA is used by bodybuilders and is thought to promote muscle growth and fat loss. The medical regulator MHRA recommended products containing DMAA be removed from sale as they pose "potential risks to public safety."
Dr Nicola Drake, an A&E consultant at St Thomas' Hospital, said DMAA had been linked to the deaths of US soldiers.
"It would give someone a racing heart, increasing heart rate and make the heart work much harder than it naturally would.
"I didn't know much about it at the time, but from research we did on the day Claire died I know it has been associated with deaths in America of soldiers doing extreme exercise."
DMAA has also been linked with high blood pressure, headaches, vomiting and strokes.
Miss Squires' boyfriend Simon Van Herrewege said she had bought a tub on the internet two or three months before running the marathon.
He told the inquest: "She never really got on with it. I don't think she particularly liked it, but she said for the marathon she wanted to beat her previous time.
"She said she was going to take one scoop of it in her water bottle and if she hit a wall she would take it to give her a boost."
Mr Van Herrewege said: "She was very active. She would regularly run a number of miles at weekends and exercised at least five days a week. She knew what she was doing."
Donna Tucker, an off-duty paramedic, was there supporting a colleague when she saw Miss Squires collapse on Birdcage Walk, near Buckingham Palace.
She said: "I saw a female with dark hair in a ponytail and a blue T-shirt on with the name Claire go past me.
"She appeared tired and was slowing down. I called Claire's name to encourage her.
"She made eye contact as she started to run again. But then she slowed down suddenly and started to struggle towards the barrier reaching out with both hands in an attempt to steady herself.
"At this point Claire appeared to have a very mild seizure which lasted about five seconds."
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