Yuliya Efimova has claimed that she was not told meldonium was to be banned ahead of her drug-test failure.
Russia's four-time world champion swimmer is one of the most high-profile names to have tested positive for the heart attack drug only added to the World Anti-Doping Agency (WADA) banned list on January 1 and has caught out a spate of athletes.
In what many will see as a weak excuse, the 23-year-old has pleaded ignorance and pointed the finger at sporting governing bodies.
"I have not received any notifications that meldonium will be included in the list of banned substances from 1 January 2016, not even one," she told Russian TV channel Rossiya 24 today.
"Neither from Russian nor from international organisations.
"Neither in the electronic form nor verbally."
Efimova won the 100 metres breaststroke title at last year's home World Championships in Kazan and is considered Russia's leading swimmer.
She won the 50m world title in 2009 and the 50m and 200m double in 2013, and also won an Olympic bronze medal over 200m at London 2012.
Efimova has already served a 16-month ban for doping having failed for banned steroid DHEA in 2013.
She claimed to have inadvertently taken the substance from a supplement she bought at a store in California and was stripped of her five titles from the 2013 European Shortcourse Championships in Herning.
The swimmer, who claims to have taken meldonium for medical reasons, said she still hopes to compete at this year's Olympic Games in Rio de Janeiro.
"I categorically reject accusations of doping use," said Efimova.
"We are currently preparing for hearings of my case.
"We intend to insist on all accusations to be lifted and prove that I did not violate anti-doping rules."
Efimova has been based predominantly in the United States since 2011, like compatriot Maria Sharapova, the tennis player who failed a meldonium test at the Australian Open in January.
She could be facing a lengthy ban for a second offence, with a lifetime suspension mentioned in some reports.
"At the moment we are waiting for news from the US Anti-Doping Agency regarding the sample taken on February 24," added her agent Andrey Mitkov.
"Secondly, we are getting ready for International Swimming Federation hearings.
"We’ll wait and see.
"It is to be hoped it will be all over."
More than 100 athletes have failed for meldonium so far, with some claiming that they stopped taking the substance prior to January 1 and had not done so afterwards.
In what could be a boost to these claims, Latvian manufacturer Grindeks has told Reuters that it can take "several months" to leave the body.
This could depend on a variety of factors such as dose, duration of treatment and sensitivity of testing methods.
WADA added meldonium to the banned list after claiming there was evidence that it was being used for performance enhancing purposes.
There are claims it was given to Soviet Union soldiers during the Afghanistan War in the 1980s in order to boost endurance.