Stay up to date with the latest news
Subscribe to our telegram channel
OCA medical committee chairman Dr Mani Jegathesan said the presence of the drug in the athlete's urine sample had been deemed "sufficient for us to take action".
"The athlete has been disqualified from the competition as well as these Games and his performance in the competition has been nullified, his medal withdrawn and appropriate adjustment made to the results," Jegathesan said.
Methylhexaneamine, commonly used in nasal decongestants, was added to the World Anti-Doping Agency's banned list this year. It can also be found in bodybuilding and dietary supplements.