Australian walker Kim Mottrom has failed to overturn a two-year suspension for using a banned substance.
Mottrom, an ex-national 50km champion, was sanctioned for using dextran and his ban was upheld by the Court of Arbitration for Sport (CAS) on Wednesday.
Mottram has served the ban, which was backdated to the start of his provisional suspension in 2014.
He will have to return his national 2013 championship medal, Australian Sports Anti-Doping Authority (ASADA) said.
"It is the first time an athlete has been sanctioned for using dextran anywhere in the world," ASADA said in a statement.
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"And ASADA's success in proving the violation was ultimately determined by complex scientific evidence.
"Dextran is a prohibited substance because it increases the amount of oxygen carried by blood cells, and can be a masking agent for steroids."
Scientific testimony showed Mottrom's level of dextran to be 26 times higher than the level permitted under the World Anti-Doping Code, ASADA said.
"In handing down its decision, CAS found that 'no expert accepted the significant level of dextran found analytically could have been absorbed orally'.
"CAS was 'comfortably satisfied on the evidence the dextran detected in the athlete's sample was by intravenous administration'," the statement said.
