Maria Sharapova announced on Monday that the drug was found in her system
The revelation that tennis star Maria Sharapova failed a drug test has put the substance at the centre of the controversy, Meldonium, in the spotlight.
Sharapova revealed on Monday night that she failed a drugs test at the Australian Open in January. She was knocked out in the quarter-finals by eventual runner-up Serena Williams.
What is Meldonium?
Meldonium is used to treat angina and heart problems. During her announcement Sharapova referred to a family history of diabetes and said she had been taking the drug for ten years because of that and numerous health issues.
The drug is made by the Latvian company Grindeks and is widely exported to Russia, where Sharapova is from, and several neighbouring countries as a drug for people with heart conditions. It is also offered for sale online. The manufacturer's website says Meldonium gives sufferers of heart and circulatory conditions more "physical capacity and mental function" - and a similar boost to healthy individuals.
How was it banned?
The drug, which is also known as Mildronate, was added to the World Anti-Doping Agency's banned list in January. It had been on the organisation's monitoring programme throughout 2015.
WADA announced the decision on its website more than three months before the ban came into force, and it was also announced by the Russian anti-doping agency. Sharapova said she received an email from WADA linking to this information, but did not read it at the time.
Sharapova's last Grand Slam win came at the French Open in 2014. Picture by: Michel Euler / AP/Press Association Images
Why was it banned?
A WADA spokesman said on Monday that Meldonium was added to its Prohibited List because of evidence athletes were using it "with the intention of enhancing performance". Studies have suggested the drug can increase a person's capacity for physical exertion.
There are signs a sizable minority of athletes were using it before it was banned. In October, the anti-doping group Partnership for Clean Competition said Meldonium was found in 182 of 8,300 urine samples from athletes as part of a study. It is not approved for use in the US, where Sharapova is based.
Who has tested positive?
Sharapova was the second Russian sportswoman to announce a positive test for Meldonium on Monday. Figure skater Ekaterina Bobrova told Russian agency R-Sport that she had tested positive at January's European Championships, and was ruled out of the World Championships as a result. Russian cyclist Eduard Vorganov also tested positive last month.
Swedish media reported that same month that former world champion 1,500 metre runner Abeba Aregawi had tested positive for the drug. There have also been two other cases involving Ukrainian biathletes.