Nijel Amos, a 2012 Olympic silver medalist in the men's 800 meters, has been banned for three years for doping, the Athletics Integrity Unit said in a ruling published on Wednesday.
The runner from Botswana tested positive for the banned substance GW1516 last year in the run-up to the track world championships and received a reduction on the standard four-year ban because he admitted to the charges.
The ban rules Amos out of next year's Paris Olympics. Amos equalled the third-fastest time in 800m history at the age of 18 when he won the silver medal behind world record-breaking David Rudisha of Kenya at the 2012 London Games, becoming Botswana's first-ever Olympic medallist.
His silver medal is not affected by the doping ruling. The 29-year-old Amos is a three-time Olympian who has won titles at the African Championships and Commonwealth Games. His time of 1 minute, 41.73 seconds from the 2012 Olympics remains the world junior record.
The AIU ruling said Amos initially asked for tests to be run on a supplement he had been taking before the positive test.
No traces of GW1516 were found in either the bottle he had used or another, unopened bottle of the same supplement, the AIU said, adding Amos then signed a form admitting to the doping charges. GW1516 was developed to help build endurance and burn fat but was found to cause cancer during tests on rodents.
Anti-doping organizations have warned athletes not to use it on safety grounds. It has been found in doping cases in various sports and also led to a ban for another 2012 Olympic medalist, Russian racewalker Elena Lashmanova.