The doping cases of tennis stars Jannik Sinner and Iga Swiatek have been making headlines. Here's an update on where both cases stand.

What substance did Jannik Sinner test positive for? On March 10, 2024, during the BNP Paribas Open in Indian Wells, California, and again out of competition on March 18, Sinner tested positive for prohibited substance clostebol, a synthetic anabolic-androgenic steroid (AAS), via urine samples. In both tests, "low levels" of the drug were detected, less than one billionth of a gram. The March 10 sample contained 86 picograms/liter while the March 18 sample contained 76pg/liter.

What explanation did Sinner give for the positive tests? Sinner said the substance entered his system unintentionally as a result of a massage from his physiotherapist, Giacomo Naldi, who had been applying over-the-counter spray Trofodermin, containing clostebol, to his own skin to treat a small wound. The medication was purchased by Sinner's fitness coach, Umberto Ferrara, in Italy where treatments containing clostebol are readily available over the counter.

What rulings have been made in the Sinner case? Sinner was provisionally suspended from tennis on April 4 after those test result findings for violating Article 2.1 and Article 2.2 of the Tennis Anti-Doping Programme (TADP). He then lodged an appeal to the International Tennis Integrity Agency (ITIA) -- the sport's worldwide anti-doping agency -- and was allowed to continue playing. He lost the $325,000 and 400 points that he had earned at the tournament in Indian Wells.

On Aug. 15, an independent tribunal commissioned by the ITIA and arbitrated by Sport Resolutions absolved Sinner of his doping charges. At the hearing, three scientific experts accepted the world No. 1's claim and found it was a credible explanation that he had been inadvertently contaminated with the substance via the physiotherapy treatment. The ITIA pointed to Article 10.5 of the Tennis Anti-Doping Programme, agreeing Sinner bore "no fault or negligence" in testing positive twice, given the treatment was administered by his physiotherapist. Sinner was cleared of any wrongdoing and avoided a doping ban.

Could Sinner be facing a tennis ban? Yes. WADA is seeking a period of competition ineligibility between one and two years for Sinner's positive doping tests. Crucially, WADA is not looking to disqualify any of Sinner's results beyond Indian Wells.

When are we likely to have an answer on the Sinner case? The Court of Arbitration for Sport announced Friday that it has scheduled a closed-door hearing April 16-17 at its headquarters in Lausanne, Switzerland.

What substance did Iga Swiatek test positive for? On Aug. 12, Swiatek tested positive in an out-of-competition sample for low levels of the prohibited substance trimetazidine, a non-specified anti-anginal medicine often used to treat heart-related conditions.

What explanation did Swiatek give for the positive test? Swiatek said she discovered that a non-prescription melatonin medicine manufactured and regulated in her native Poland contained the substance. She had been taking the sleep medication "for jet lag and sleep issues," and did not hold a valid Therapeutic Use Exemption (TUE) prior to her positive test.

What ruling has been made in the Swiatek case? The ITIA sent Swiatek a pre-charge notice of an anti-doping rule violation immediately after testing positive for the banned substance. Findings for such non-specified substances carry a mandatory provisional suspension, which was subsequently handed down by the ITIA on Sept. 12.

On Sept. 22, Swiatek appealed the provisional suspension. Days later, she learned her sleep medication was responsible for her contamination and informed the independent tribunal chair. The contamination was confirmed by the independent and WADA-accredited Sports Medicine Research & Testing Laboratory in Utah.

The independent tribunal chair lifted the provisional suspension on Oct. 4. Swiatek accepted a one-month sanction and completed her period of ineligibility on Dec. 4, after having returned to the court for the WTA Finals and Billie Jean King Cup finals.

Does this mean the Swiatek case is now closed? Not just yet. It's possible WADA could still lodge an appeal, as has been done in the Sinner case. However, such action is growing increasingly unlikely given it lodged its appeal for Sinner within a week of the ITIA's findings being published. Swiatek and her camp do not anticipate WADA to appeal.