US sprinter Calvin Harrison has been suspended for two years after being found guilty of a doping violation.
Harrison said he was given the substance by a coach in California
As a result he becomes ineligible for the Athens Olympics.
Harrison, a gold medallist in the 4x400m relay in Sydney, tested positive for the banned stimulant modafinil at the 2003 US championships.
The US team could also lose world 100m champion Torri Edwards, who faces a two-year ban after testing positive for a banned stimulant in April.
Harrison, who also tested positive for a banned stimulant in 1993, will now have all his results from the time of the second positive drug test nullified.
As a result, he is set to lose his relay gold medal from last year's world championships in Paris, where France won silver.
The IAAF is already currently considering whether to strip the US squad of its gold medal at the Sydney Olympics.
The title could be forfeited because one member of the team, Jerome Young, failed a steroid test in 1999.
The Swiss-based Court of Arbitration for Sport ruled in late June that Young should be stripped of his relay medal and the IAAF has recommended that the entire team - including Michael Johnson - be stripped of its medals.
A final decision rests with the International Olympic Committee, which is expected to rule days before the Athens Games and is expected to endorse the IAAF recommendation.
Harrison's lawyer, Edward Williams, said he did not know
whether his client would appeal against the decision, made by a
three-member panel of the American Arbitration Association
(AAA)/North American Court of Arbitration for Sport (CAS).
"He's disappointed, particularly about the fact that the
arbitrators didn't essentially nullify the repercussions of the first offence, which dealt with pseudoephedrine, which is no longer on the (banned) list... It was then but is not now," Williams said.
Williams also said Harrison's due process was denied in the 1993 hearing process.
The lawyer was also disappointed that the hearing
panel did not accept the testimony of his expert witness, a pharmacologist once employed by the manufacturer of modafinil, that the drug was not a stimulant.
Harrison's twin brother, Alvin, also faces a lifetime ban after being charged by USADA with steroid use, despite never having tested positive.
His case is currently awaiting arbitration.