Abuse of meldonium by elite athletes forced the hand of the World Anti-Doping Agency, leading sports doctor Peter Brukner says.

Meldonium – the banned substance that Maria Sharapova announced she had tested positive for on Tuesday – can aid athletes in endurance and recovery and protect against stress.

The Russian tennis star said she had been taking meldonium for 10 years because she had a magnesium deficiency and a family history of diabetes, but the revelations sparked a tirade from former pro Jennifer Capriati, who said drug use could have prolonged her career.

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Meldonium is usually prescribed by a doctor to treat reduced blood flow to the heart, such as for sufferers of angina and myocardial infarction.

But its rising use among athletes raised eyebrows at WADA, who decided to monitor tests in 2015 for the substance, before adding it to their banned list – effective from January 1, 2016.

Dr Brukner, who is now working with the Australian cricket team and is a professor of sports medicine at La Trobe University, says that athletes were using it to aid performance.

Sharapova says there are mitigating factors for taking the substance. Photo: Getty

“It [meldonium] has only become popular over the last couple of years,” he told The New Daily.

“WADA found quite widespread use of the drug in elite sport in Europe and that promoted them to add it to the banned list.

“Clearly, it has been used as a performance enhancer up until now. She [Sharapova] is not the only one who has tested positive. I suspect there will be a few more.”

Dr Brukner said ignorance was simply no excuse for Sharapova, who claimed she did not know meldonium was banned after testing positive at January’s Australian Open.

He believes Sharapova can expect a four-year ban from tennis.

“It is going to be very difficult for her to avoid the four years,” he added.

“There is a couple of scenarios which can reduce it [a ban] – one is that you have a genuinely inadvertent doping case, but while she may have been unaware of its status, she certainly knew what she was taking.

“I don’t think she can argue that point – I think she is going to get four years.”

Swiss watch company TAG Heuer announced on Tuesday evening (AEDT) that it was severing ties with Sharapova, following Nike’s decision earlier in the day to suspend its sponsorship deal with the tennis star.

The 2010 Nike deal is believed to be worth $US70m over eight years.

Dual Australian Open champion Jennifer Capriati called for Maria Sharapova to be stripped of all her titles. Photo: Getty

News of Sharapova’s positive test was greeted with shock by fans and disgust from at least one former player.

Two-time Australian Open champion Capriati savaged Sharapova for her use of a banned substance in a spectacular Twitter rant.

Capriati, whose career was cut short by injury after winning two Australian Open titles and the 2001 French Open, is livid at Sharapova’s confession that she tested positive.

The American said she was furious because she felt her career ended prematurely in part because she refused to cheat.

“I had to throw in the towel and suffer,” Capriati posted on Tuesday.

“I didn’t have the high priced team of [doctors] that found a way for me to cheat and get around the system and wait for science to catch up.

“What’s the point of someone taking a heart medicine that helps your heart recover faster unless you have a heart condition? Is that accurate?

“It’s always about one thing that benefits everyone. #money

“Maybe I should start taking it? Lol I might feel better.”

Sharapova faces a lengthy suspension and has already been provisionally banned from March 12 after testing positive during the Australian Open.

Capriati continued her social media rant by saying the Russian should be stripped of her 35 professional titles, which includes two French Opens (2012, 2014), the 2004 Wimbledon championship, 2006 US Open crown, and the 2008 Australian title.

If this medication helped me to comeback again would everyone be alright with me taking it?

— Jennifer Capriati (@JenCapriati) March 7, 2016

TENNIS’ CHEQUERED HISTORY WITH DRUGS

Andre Agassi: The eight-time grand slam winner revealed in his compelling autobiography, Open, that he failed a 1997 drug test after taking crystal meth. He said he accidentally took the drug – and tennis’ governing body believed him. It remained a secret until the release of his book.

Martina Hingis: The Swiss star tested positive for a metabolite of cocaine in 2007. The level found was minimal – and she appealed – but she still received a two-year suspension. Hingis had, by then, already retired once, and another break followed before she returned to the doubles circuit.

John McEnroe: In 2004, the former world No.1 said that for a six-year period during his playing career, he was given steroids – without his knowledge – to treat pain. McEnroe, who was insistent the drugs were anti-inflammatories, said the steroids he was taking were later judged as ‘too strong’ for horses.

Mats Wilander: In May 1997, the Swedish star received a three-month suspension for a positive test to cocaine in 1995. Wilander initially lodged an appeal and claimed that the drug was unknowingly consumed. But he eventually withdrew that appeal, accepting the punishment. He returned to tennis as a coach in the 2000s.

Jennifer Capriati: The American, who has had a string of off-court incidents, was arrested in May 1994 and charged with marijuana possession. She was just 18 then and entered a counselling program. Capriati was particularly vocal in her criticism of Sharapova after the Russian’s positive test hit the news.

Richard Gasquet: Suspended in May 2009 for a year for testing positive to cocaine, the Frenchman was cleared to play two months later. He appealed the case to the Court of Arbitration for Sport (CAS), arguing a kiss with a woman in a nightclub was responsible for his positive test. He was cleared and is now ranked 10th in the world.

Marin Cilic: Traces of the banned stimulant nikethamide were found in a 2013 sample from Cilic. The Croatian was banned for nine months initially. He claimed his test was due to glucose tablets and later had the punishment reduced to four months by CAS. He won the 2014 US Open and is currently ranked 12th.

Petr Korda: The left-hander, who won the 1998 Australian Open, tested positive for banned steroid nandrolone at Wimbledon later that year. His love for veal was reportedly given as an excuse – young calves are fattened by the steroid – but it was said that Korda would have had to consume 40 animals per day to record a similar level on a test.

Viktor Troicki: Refusal to take a blood test in 2013 saw Troicki banned for 18 months. He appealed, and his suspension was reduced to one year. He claimed on the day of his test that he had a needle-phobia and was feeling poorly. The Serb had a strong ally in Novak Djokovic but despite his protestations, he remained banned.

Greg Rusedski: The Canadian-born Brit revealed to media at the 2004 Australian Open that he had tested positive for banned steroid nandrolone at an event the year before. The news rocked the tennis world but he was soon cleared, with the drug contained in contaminated pills given to him by ATP trainers.

Wayne Odesnik: The American was first banned when he pleaded guilty to importing human growth hormone into Australia. He was suspended for two years in March 2010, but it was reduced to one due to his cooperation. He was banned again, this time for 15 years, in 2014, due to a positive test for many banned substances.

Barbora Strycova: Then known as Barbora Zahlavova-Strycova, the Czech player was banned for six months for a positive test to stimulant sibutramine. She claimed the test was because of a slimming product. Her ban was backdated, meaning she missed very little tennis.

-with ABC