"I categorically reject the doping accusation," Efimova said in a home video posted on her official Facebook page. "We are currently preparing for a hearing of my case.
We intend to have the accusations completely dismissed and prove that I didn't violate anti-doping regulations."
Efimova, who was suspended for 16 months and stripped of five European titles after testing positive for an anabolic steroid in 2013, could face a lifetime ban if found guilty of a second career doping code violation.
The 23-year-old swimmer, who won a bronze medal in the 200-metre breaststroke at the 2012 London Games, conceded she had taken meldonium for medical reasons before the World Anti-Doping Agency's (Wada) ban on the drug came into effect on January 1.
