The Latvian inventor of meldonium on Friday insisted the drug was safe and questioned whether authorities were justified in listing it as a performance enhancer.

Russian tennis superstar Maria Sharapova is facing a potentially career-ending four-year ban after she tested positive for the Soviet-era drug at the Australian Open.

Inventor Ivars Kalvins, 68, of Latvia's Institute of Organic Synthesis, told AFP that the medicine also known as Mildronate is "the safest cardio-vascular drug in the world."

The drug, manufactured in Latvia, dates from the Soviet Union in the 1970s. It is used to treat ischaemia, a lack of blood flow to parts of the body.

The increase in blood flow it produces could improve endurance and recovery time after exercise.

Kalvins told AFP "there is no evidence that Mildronate would correspond to the three requirements needed to include a medicine on the list of banned substances...

"Nobody has demonstrated that it is an enhancer or performance booster. The only evidence is anecdotal.

"If they want to say it is a booster there should be clinical evidence -? but it does not exist."

Sharapova maintained she took the drug for health reasons, and not as a performance enhancer, and was unaware it had been banned by doping watchdogs at the start of the year.

Meldonium sales have more than doubled in Russia since she admitted to taking the substance, which is not available in Western Europe.

Kalvins said he suspects the ban may be connected to this year's Olympic Games in Brazil.

"The reason (for the ban) mainly is that the Olympic Games are coming. Some of the competitors should be excluded from the competition," he told AFP.

Asked by AFP whether he thought the ban was created to prevent Russian athletes from competing in the Olympics, Kalvins said: "I think so."

Kalvins also said China is manufacturing the drug.

"You can read it in their literature -? publications in China about clinical trials published by Chinese military hospitals... They told me the army used it," he told AFP.

The World Anti-Doping Agency (WADA) said on March 11 it had recorded 99 positive tests for meldonium since January 1.

WADA moved meldonium from its "monitored" to "prohibited" list at the start of 2016 "because of evidence of its use by athletes with the intention of enhancing performance."

Meanwhile, the mayor of Riga, Nils Usakovs has turned the controversy over the drug into a cheeky promotional initiative.

On his Twitter and Instagram accounts, he has mocked up a holiday-style poster, decorated with swimsuit-clad women, with the slogan: 'Welcome to Riga, meldonium home city!'
Source: AFP