( CNN) The origins of meldonium, the banned narcotic used by Russian tennis player Maria Sharapova, are shrouded in Soviet-era secrecy. Sharapova has been suspended for two years by the International Tennis Federation after testing positive for meldonium,

Back in the Soviet Union's heyday, scientists tested meldonium on athletes in clandestine state-run labs, according to Ivar Kalvins, the Latvian chemist who devised the narcotic.