LONDON: The medicine Maria Sharapova says she has taken for 10 years due to a family history of heart issues and diabetes is an old drug sold in just a few Eastern European countries that can also boost exercise tolerance.

The tennis star tested positive for the banned drug meldonium, or Mildronate, in a sample taken on January 26, the day of her Australian Open quarter finals defeat to Serena Williams.

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.

The 28-year old Russian, a five-time grand slam champion and the highest paid woman in sports, will be provisionally suspended starting March 12, the International Tennis Federation (ITF) said.

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 trains, which have full regulatory backing and years of robust safety and efficacy data.

LATVIAN DRUG

Meldonium is cheap and available over the counter without a prescription in some eastern European countries, where it is marketed as Mildronate by the Latvian pharmaceutical firm Grindeks (GRD1R.RI).

It reduces the level of a metabolite called carnetine in muscles, and by doing that helps muscles cope better with high levels of stress and low oxygen levels.

"Because it effects the cellular metabolism, it would increase energy production within cells and therefore make oxygen utilization more efficient," said Pirmohamed.

In a 2010 academic paper published in a review journal called Seminars in Cardiovascular Medicine and cited on the Grindeks company website, it has been shown to improve exercise tolerance in patients with heart problems.

The World Anti-Doping Agency, which banned the drug in January after previously having it on a "watch list", ranks it as a prohibited metabolic modulator and cites "evidence of its use by athletes with the intention of enhancing performance."

Grindeks says the drug could protect athletes from cell damage, but says it would be unlikely to improve their competitive performance.

It would be "reasonable to recommend (sports people) to use meldonium as a cell protector to avoid heart failure or muscle damage in case of unwanted overload," the spokeswoman said.

Athletes "should not expect increase of physical capacity, but, for sure, they will be protected against ischemic damages of cells in case of overload."