Russia's Maria Sharapov failed a drugs test at this year's Australian Open due to a substance she has taken for 10 years for health issues, and has been banned for two years. But why is meldonium on the banned list?
The substance in question is known as meldonium, and was placed on the WADA banned list only at the start of the year.
Since then a number of athletes have tested positive for it: Russian cyclist Eduard Vorganov, Russian figure skater Ekaterina Bobrova, Ethiopian-born athletes Endeshaw Negesse and Abeba Aregawi, and Ukraine biathletes Olga Abramova and Artem Tyshchenko.
What is meldonium and what does it do?
Also known as mildronate, meldonium is used to treat chest pain and heart attacks among other conditions.
The drug works by treating ischaemia, a lack of blood flow to parts of the body. It dilates blood vessels and increases blood flow.
It is made in Latvia and licensed in several European countries - including Russia - though it is not approved for use in the USA
Why is it banned?
It is listed by WADA as an 'S4' substance, along with other prohibited metabolic modulators including insulin, as some researchers say it can also help recovery.
Researchers have also linked it to increased athletic performance and endurance.
WADA made the decision to ban it last September, with the decision coming in to force on January 1st. The organisation cited "evidence of its use by athletes with the intention of enhancing performance" when it introduced the ban.
According to the US National Library of Medicine (as cited by health24.com), it improves users' mood and allows them to become more active.
Why was Sharapova taking it?
Sharapova claimed in her press conference that she has a family history of diabetes, and was taking the substance as part of her medication to combat it for almost a decade.
"I was first given this medicine by my doctor for several health issues I was having back in 2006," explained Sharapova.
"I was getting sick a lot. I was getting the flu every couple of months. I had irregular EKG results.
"I had a deficiency in magnesium and a family history of diabetes, and there were signs of diabetes.
"That is one of the medications, along with others, that I received."
Maria Sharapova blows a kiss towards her fans
Image credit: Reuters
Sharapova takes full responsibility
"I received a letter on 22 December from WADA for the changes next year and where the tests will be with a link to the changes for 2016, and I did not look at that list.
"It is very important for you to understand that for 10 years this medicine was not on WADA's banned list and I had been legally taking that medicine for the past 10 years.
"But on 1 January the rules had changed and meldonium became a prohibited substance, which I had not known...
"I made a huge mistake. I let my fans down and I let the sport down.
"I take full responsibility for it. I know that with this I face consequences and I don't want to end my career this way. I really hope that I will be given another chance to play this game."
Sharapova: 'I know I face consequences... I hope I'll be given another chance'