Maria Sharapova has revealed she failed a drug test for meldonium at January's Australian Open - but what is the substance?
The Russian tennis player, who burst onto the scene in 2003 at the age of 16, made the revelation at a press conference yesterday.
Sharapova said that she had been taking the substance since 2006 - and it was only added onto the World Anti-Doping Agency's (WADA) banned list at the start of this year.
What is Meldonium?
*Meldonium is also known as Mildronate, the name by which Sharapova knew the drug having taken it since 2006.
*It is commonly used to treat angina, other heart problems and diabetes. Sharapova referred to a family history of diabetes during her announcement yesterday.
* Despite only being added to the list this year, meldonium has been on the organisation's monitoring programme throughout 2015.
*A WADA spokesman said on Twitter yesterday: "Meldonium was added to Prohibited List because of evidence of its use by athletes with the intention of enhancing performance." Studies have also indicated that the drug can increase an individual's capacity for physical exertion.
*The drug is manufactured by Latvian company Grindeks and widely exported to Sharapova's homeland of Russia and several neighbouring countries. However, it is not approved for use in the United States, where the tennis player has her base.
*Sharapova was the second Russian sportswoman to announce a positive test for meldonium on Monday. Figure skater Ekaterina Bobrova confirmed to 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.
The five-time grand slam champion has not yet been told what sanction she faces but has accepted a provisional ban from the sport.
Last night, she added that she "did not want her career to end like this".
Today, it has been announced that watchmaker Tag Heuer has decided not to renew its sponsorship contract with Sharapova, following her announcement about the failed test.
The company follows Nike, which has suspended its current contract with the champion.
Tag Heuer's statement read: "Maria Sharapova was under contract with TAG Heuer until December 31, 2015. We had been in talks to extend our collaboration.
"In view of the current situation, the Swiss watch brand has suspended negotiations, and has decided not to renew the contract with Ms Sharapova."