The issue emerged at the Australian Open, where Sharapova reportedly tested positive for use of a drug called meldonium. Manufactured in Latvia and prescribed in many former Soviet Bloc countries, meldonium is used to treat heart conditions and improve cardiac circulation. It is not approved by the FDA for use in the United States, and the World Anti-Doping Agency added it to its list of prohibited substances at the start of this year.
Sharapova admitted that she's been taking the medication for ten years now but that she did not keep up to date on the WADA's list. Since it is considered a prohibited substance, she's been excluded from participating in the Australian Open this year, and suspended from competition as of March 12. She was also scheduled to take part in the Porsche Grand Prix, a tennis event sponsored by the carmaker in Stuttgart next month which she will now apparently have to miss.
One of the top-rated female tennis players in the world, Sharapova has served as a brand ambassador for Porsche since 2013. Other sponsors including TAG Heuer and Nike have also reportedly suspended their relationships with the athlete pending further investigation by the International Tennis Federation.