RIGA: Latvia expressed sadness on Wednesday over the banning of the drug that has cast a pall over the career of tennis star Maria Sharapova, describing it as "one of the most significant accomplishments" of the tiny nation's scientists.

The five-time grand slam champion has revealed she tested positive in January for the drug meldonium, which its Latvian inventor once said had been used to toughen up Soviet troops fighting at high altitudes three decades ago.

Latvia, a Baltic nation of under 2 million people that won independence from the Soviet Union in 1991, is relatively unknown to outsiders apart from visitors who use the capital Riga as a destination for partying.

So meldonium, which is marketed as Mildronate by the Latvian pharmaceutical firm Grindeks, is a source of some national pride.

"It's sad that there is such a situation, that this drug has been banned," said Andrejs Vaivars, a spokesman for Prime Minister Maris Kucinskis. "Especially given that is one of the most significant accomplishments of Latvian scientists in general."

Meldonium, which is available cheaply over the counter without a prescription in the Baltic states and Sharapova's native Russia, is normally used to treat heart conditions such as angina.

But the drug, which boosts blood flow and may enhance athletic performance, was banned by the World Anti-Doping Agency (WADA) as of Jan. 1. Sharapova said she had missed an email informing her about the ban.

Scientist Ivars Kalvins invented the drug in mid-1970s when Latvia was still a Soviet republic. Kalvins told the local newspaper Diena in 2009 that it had been used to boost troops' fighting stamina in the 1980s. At that time Soviet forces were battling insurgents in Afghanistan.

"There are high mountain conditions, lack of oxygen," Kalvins said. "They were all given Mildronate. They didn't know what they were using themselves. Nobody asked them anything back there."

Kirovs Lipmans, chairman of Grindeks and its biggest shareholder, said use of the drug did not constitute doping and he criticised the government for not defending its reputation against WADA.

"The government is not fighting against it, it is not doing anything, they are absolutely not interested in this. How can they act like that?" said Lipmans, who also heads the Latvian Ice Hockey Federation and is a member of the country' Olympic Committee. Government officials said WADA was acting independently and they could not influence its decisions. Grindeks is seeking to register Mildronate in China, and Lipmans said he would like to see it also registered in the future in western Europe. The company has said it was looking to diversify its sales as its revenues in Russia were hit by the fall in rouble.