The Latvian creator of banned drug meldonium said on 10 March that he was "quite sure" other top athletes are – and should – use it. Ivars Kalvins expressed sadness 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. Kalvins also claimed that Sharapova is not alone in taking the drug, which was only added to the banned list on 1 January 2016.

Kalvins said: "I am quite sure that a lot of athletes at the top level are using mildronate [meldonium] – and they should use mildronate to protect themselves in case of overloading. Because if there is overloading then the cardio muscle, cells will die out because [of the] lack of oxygen there. In the case of using mildronate these cells will survive. And this is like an insurance, insurance that sportsman will not die on the field of their sport event."

Kalvins invented the drug in mid-1970s when Latvia was still a Soviet republic. He told 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. 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. The drug, which is marketed as mildronate by the Latvian pharmaceutical firm Grindeks, is a source of some national pride.

But the drug, which boosts blood flow and may enhance athletic performance, was banned by the World Anti-Doping Agency (Wada) as of 1 January 2016. Sharapova said she received an email about the list of banned drugs but failed to click on the link which listed them. She said her family doctor had first given her the drug 10 years ago after she frequently became sick, had irregular electrocardiogram results, a magnesium deficiency and a family history of diabetes.

"If Sharapova would not [have] used mildronate for 10 years, probably she would have discontinued her career five years ago, or four years ago or six years ago, who knows?" Kalvins said. "This is not increasing performance, but insurance that if you will go over your body's boundaries, you still will be kept healthy," he added.

For the health conditions Sharapova says she has, however, doctors say the scientific evidence for mildronate is limited compared with many medicines widely available in Europe and the United States, where Sharapova lives and trains, which have full regulatory backing and years of robust safety and efficacy data. Kalvins says he has not yet seen the scientific, clinically tested proof that mildronate should be banned as doping.

"If there is no scientific evidence or scientific background, why has it happened after 32 years of being on market as the safest cardio-vascular cardio protector? There is only one other option: there are some political reasons for it," he said.

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. Government officials said Wada was acting independently and they could not influence its decisions.