As the tennis world reacts to the news Russian champion Maria Sharapova tested positive to a banned substance at the Australian Open this year, the manufacturer of the drug has raised more questions.

The Latvian company behind drug meldonium – which is designed to treat lack of blood flow to parts of the body, particularly in cases of angina or heart failure – said regular treatment lasted four to six weeks, rather than the 10 years Sharapova said she had been taking the drug.

“Depending on the patient’s health condition, treatment course of meldonium preparations may vary from four to six weeks. Treatment course can be repeated twice or thrice a year,” the company said in a statement on Tuesday.

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Sharapova said she was first given the drug in 2006 to treat a number of health conditions she had at the time, including the early signs of diabetes and irregular ECG (heart sonogram) tests.

The world number seven is the world’s highest-paid athlete. Photo: Getty

It is not known whether Sharapova used the drug constantly over 10 years or if she completed a number of smaller treatments.

After the story broke, world number one Serena Williams praised Sharapova for showing courage in yesterday’s highly-publicised press conference.

“I think most people were surprised and shocked by Maria, but at the same time I think most people were happy that she was upfront and very honest and showed a lot of courage to admit to what she had done and what she had neglected to look at,” said Williams.

“As Maria said, she’s ready to take full responsibility and I think that showed a lot of courage and a lot of heart, and I think she’s always showed courage and heart in everything she’s done and this is no different.”

While some weren’t willing to believe Sharapova didn’t know the drug had entered the banned list, the athlete’s former coach Jeff Tarango said her team was likely to blame.

Tarango said it was “believable” Sharapova had not read the email regarding meldonium, and that her entourage should have taken care of it for her.

Despite tennis’ governing body not yet handing down an official suspension for Sharapova, the 28-year old was temporarily dropped by major sponsors Nike, watchmaker Tag Heuer and Porsche following Tuesday’s announcement.