Efimova, the 100 metres breaststroke champion at last year's home FINA World Championships in Kazan, had been hoping she would be free to compete again following the announcement by the World Anti-Doping Agency (WADA) on Wednesday (April 13) that they were reviewing cases involving meldonium.

WADA ruled that if below one microgram of the heart medication, only added to the prohibited list on January 1, was detected in a test before March 1, a no fault or negligence verdict could be reached.

The organisation admitted "limited data exists to date" on the urinary excretion of the drug, while the renal elimination of meldonium is expected to "vary significantly between individuals, depending on the dosing and duration of the drug administration protocol".

Following the announcement, the 24-year-old Efimova had written to FINA asking for her current temporary suspension to be removed so that she could compete at Russia’s Olympic trials, due to begin in Moscow later today. 

Several other Russians in other sports who have tested positive for meldonium have already had their bans lifted, temporarily at least, following WADA's announcement. 

FINA, however, has rejected her request.

"Considering the provisional suspension imposed by FINA to swimmer Yulia Efimova (RUS) and the recent WADA recommendations on the use of meldonium, the FINA Doping Panel decided to maintain the provisional suspension of this athlete, until a hearing of Ms Efimova is held by the FINA Doping Panel," they said in a short statement released early today.

Efimova's agent Andrei Mitkov revealed earlier this week that she tested positive for meldonium on four different occasions, two of them before March 1 and two after. 

FINA's decision is a blow to Efimova, Russia's best hope for a medal at this year's Olympic Games in Rio de Janeiro. 

She also won a 50m world title in 2009 and the 50m and 200m double in 2013, in addition to a London 2012 Olympic bronze medal over 200m.

If she is found guilty of using meldonium, Efimova could face a life ban from the sport.

She previously served a 16-month ban from the sport for a previous failure for banned prescription steroid DHEA in 2013.

Efimova claimed to have inadvertently taken the steroid from a supplement she bought at a store in California, where she was training, and that a salesperson assured her the supplement was "doping-free", though DHEA was clearly listed as an ingredient on the label.

Efimova was stripped of her five titles at the 2013 European Shortcourse Championships in Herning, but many criticised how her 2013 World Championships performances survived and that she was able to return in time for Kazan 2015.

Efimova has been based predominantly in the United States since 2011, like Maria Sharapova, the leading tennis player who failed a meldonium test at the Australian Open in January.

Even if FINA had agreed to lift the suspension, Efimova may still have not been able to compete as Vladimir Salnikov, President of the Russian Swimming Federation, had revealed earlier in the day he did not think she would be fit enough to take part.