• Wada admits to lack of scientific evidence regarding time drug stays in system • Sharapova among scores of athletes who have tested positive for meldonium

Maria Sharapova and scores of other athletes who have tested positive for meldonium could be handed a lifeline after the World Anti-Doping Agency said there was a lack of scientific evidence about how long the drug stays in the system.

Amid growing confusion about the status of an avalanche of positive tests for the drug, which was banned on 1 January this year, Wada said its preliminary tests showed that it could take weeks or months for the drug to leave the body. In such cases, athletes “could not reasonably have known or suspected” that the drug would still be present in their bodies after 1 January, said Wada in a “clarification paper” to its code signatories on how they should prosecute meldonium cases.

“In these circumstances Wada considers that there may be grounds for no fault or negligence on the part of the athlete,” it added. Sir Craig Reedie, the president of Wada, said: “It is designed to explain the science that we know. The issue that it deals with is the time this drug takes to come out of the system. It’s an attempt to clarify the many questions that we’ve been asked.”

The Russian sports ministry and national Olympic committee welcomed the Wada statement, and the country’s officials suggested there could be a mass amnesty of Russian athletes.

The head of the Russian tennis federation (RTF), Shamil Tarpishchev, told the R-Sport agency he hoped Sharapova would be able to play at the Olympics in Rio de Janeiro in August, while the head of the Russian swimming federation suggested there could be a swift return to competition for the suspended world champion Yulia Efimova.

A Wada spokesman said talk of an amnesty was “wide of the mark” and that the document was designed to clarify the position.

Sharapova confirmed last month that she had tested positive for meldonium during the Australian Open. She was one of 172 athletes, many of them Russian, to test positive for the drug since it was banned in January.

The Latvian-made drug, which is typically prescribed for heart conditions, was widely used as a supplement by athletes in eastern European countries. The drug increases blood flow, which improves exercise capacity by carrying more oxygen to the muscles.

Sharapova said she had been taking the drug for 10 years on medical advice and had missed various communications about the addition of the drug to the banned list. However, she could yet be undone by a supportive statement from her racket manufacturer, Head. In a statement that controversially backed Sharapova in the wake of her admission, it suggested she had carried on taking the drug after 1 January – albeit, it claimed, in quantities that were not performance enhancing.

Wada said in its briefing document that doping cases should be pursued in the case of athletes who admit having taken meldonium on or after 1 January, in cases where the concentration of the drug is above 15 micrograms per millilitre, or where the concentration is between 1 and 15 millilitres and the test was after 1 March.

The organisation said prosecution of meldonium cases could be “stayed” and provisional suspensions lifted if the concentration of the drug in the system was between 1 and 15 micrograms per millilitre and the test was carried out before 1st March, or if the level is below 1 microgram per millilitre and the doping control was conducted after 1st March.

John Haggerty, Sharapova’s attorney, hit out at Wada over the way it had handled the case. He said: “The fact that Wada felt compelled to issue this unusual statement now is proof of how poorly they handled issues relating to Meldonium in 2015. Given the fact that scores of athletes have tested positive for taking what previously was a legal product, it’s clear Wada did not handle this properly last year and they’re trying to make up for it now.

“The notice underscores why so many legitimate questions have been raised concerning Wada’s process in banning Meldonium as well as the manner in which they notified players. This notice should have been widely distributed in 2015, when it would have made a difference in the lives of many athletes.”

Sharapova was provisionally suspended by the International Tennis Federation pending a disciplinary hearing. “We can confirm that the case is ongoing and that there will be a hearing,” the ITF spokesman Nick Imison told the Associated Press. “I have seen the statement from Wada and obviously any ongoing cases will take that information from Wada, but it won’t affect the fact that there is an ongoing case.”

Tarpishchev said Sharapova’s ban could be addressed in a meeting with the head of the International Tennis Federation head, David Haggerty, later this month. “The situation with Sharapova could be resolved after 21 April when we meet with the head of the international federation. After that all should be become clear. It is too early to talk about Sharapova competing at the Olympic Games,” Russia’s Tass news agency quoted the RTF head as saying.

Professor Roger Pielke Jr, of the centre for sports governance at the University of Colorado, said he expected continued issues over levying meldonium sanctions. “Attention has focused on how long Meldonium stays in the body, but it is only a short step to asking questions about Meldonium’s performance-enhancing effects, and at different levels in the human body. I would expect that such questions are soon to follow, which Wada is not well prepared to answer,” he told the Guardian.

“The bottom line here is that robust evidence should be in hand before anti-doping regulations are put into place. Yes, this sets a rather high bar, but it also keeps anti-doping agencies accountable to science and protects the due process rights of athletes.”

In a statement, Reedie added: “There is no doubt as to the status of meldonium as a prohibited substance. There is equally no doubt that the principle of strict liability under the Code; as well as, the well established process for results management and adjudication prevail.

“Since meldonium was prohibited on 1 January of this year, there have been 172 positive samples for the substance, for athletes across numerous countries and sports. Concurrently, there has been a call by stakeholders for further clarification and guidance. Wada recognises this need – that meldonium is a particular substance, which has created an unprecedented situation and therefore warranted additional guidance for the anti-doping community.”