In its updated guidelines on the banned drug meldonium, World Anti-Doping Agency has opened the possibility that some athletes who have tested positive for the substance could have their provisional suspensions lifted. The agency issued a notice yesterday to stakeholders, saying that there is currently a lack of clear scientific information on how long meldonium stays in the body. It said there is a possibility that some athletes yielded positive drug tests despite having legally ingested the substance before its ban came into effect on January 1.Now, less than four months before the Rio Olympics, WADA's notice is expected to have a major impact on many of the 172 athletes who have tested positive for the performance-boosting drug. They include five times grand slam tennis champion Maria Sharapova, who was among 40 Russian athletes to test positive for the drug after it was added to WADA's list of banned substances in January.