Good Morning Britain's Health Editor Dr Hilary Jones has questioned Maria Sharapova's claim that her decade-long use of the drug meldonium was for "health issues".
Sharapova has said she was unaware meldonium had been banned by sports authorities in January after using the drug legally since 2006.
But Dr Jones doubted the Russian had ever used it for its prescribed use: to ward off heart failure or angina.
"There has been a string of Eastern bloc athletes; middle distance runners, cyclists, ice skaters, who have been provisionally banned for using (meldonium)," Hilary said, adding it was clear they were "using it for endurance".
Over the past month, Russian cyclist Eduard Vorganov, Russian figure skater Ekaterina Bobrova, Ethiopia-born athletes Endeshaw Negesse and Abeba Aregawi, and Ukraine biathletes Olga Abramova and Artem Tyshchenko have all tested positive for meldonium.
Sharapova said her family doctor had been giving her mildronate, which is also called meldonium, for 10 years after she frequently became sick, had irregular EKG results, a magnesium deficiency and a family history of diabetes.
The former UK anti-doping boss has said questions will be asked of Maria Sharapova's support personnel and doctor over why the tennis star was allowed to take Meldonium.
Michele Verroken told Good Morning Britain the prohibited list changes at the beginning of the calendar year and that athletes are advised three-months before so that they can revise their medications.
Meldonium is most commonly used in Russia and is not approved by the Food and Drug Administration for use in the US.
Ms Verroken said: "Questions will be asked of the athletes support personnel, the doctor in particular, who is prescribing this because now we can take sanctions against the athletes support personnel."
Nike has suspended its relationship with Maria Sharapova after the tennis star announced that she had failed a drug test.
In a statement to CNBC, the sportswear company said it was suspending its relationship with the player until the investigation is complete.
We are saddened and surprised by the news about Maria Sharapova.
We have decided to suspend our relationship with Maria while the investigation continues.
We will continue to monitor the situation.
Here's how Twitter reacted to Maria Sharapova's shocking announcement that she had failed a drugs test.Read the full story ›
The ITF have confirmed the suspension will come into affect from 12 March.
Steve Simon, the CEO of Women's Tennis Association, said he is "saddened" by the news that Maria Sharapova has failed a drugs test.
Maria Sharapova has announced she failed a drugs test at the Australian Open: what is meldonium, the drug she admits taking?Read the full story ›
Maria Sharapova has announced she failed a drugs test at the Australian OpenRead the full story ›
Andy Murray produced his most remarkable Davis Cup effort yet to hold off an inspired Kei Nishikori and send Great Britain through to the quarter-finals for a third straight year.
Murray led by two sets to love but faced losing from that position for the first time in 11 years only to grind out a 7-5 7-6 (8/6) 3-6 4-6 6-3 victory after four hours and 54 minutes at Birmingham's Barclaycard Arena.
That clinched a 3-1 first-round win over Japan for Britain, with Murray winning all three points for the fourth successive tie.
Great Britain captain Leon Smith reserved the highest praise for his main man, saying: "I'm pretty much lost for words. He's just a man of steel.
"You have to give a lot of credit to Kei. He played a great match, one of the best of his life I'm sure.
"It's quite astonishing considering Andy hasn't played since the Australian Open final. He's amazing. It's an absolute privilege to sit with him for a match like that and we'll remember that one for a very long time."
Andy Murray's appetite for another stellar Davis Cup run should see him partner brother Jamie in Saturday's doubles as Great Britain look to restore their lead over Japan.
The teams were tied at 1-1 after the first day of play at Birmingham's Barclaycard Arena, with Murray easing past Taro Daniel 6-1 6-3 6-1 before Kei Nishikori withstood a fierce challenge from Dan Evans to win 6-3 7-5 7-6 (7/3).
Murray's match was his first since becoming a father nearly a month ago and he was wary of committing to doubles as well as singles beforehand, but captain Leon Smith confirmed the plan is for the brothers to team up as they did successfully on three occasions last year.