What is Clostebol? All you need to know about the banned substance Jannik Sinner failed anti-doping tests for
World No. 1 Jannik Sinner recently got involved in a doping controversy after testing positive for Clostebol, a prohibited substance. The International Tennis Integrity Agency (ITIA) and an independent tribunal gave the Italian a clean chit, allowing him to continue his career uninterrupted.
Clostebol is an anabolic steroid that helps athletes build muscle mass, train harder, and assist in recovery following an intense workout. In humans, it is approved for dermatological and ophthalmological use. Clostebol has a similar chemical composition to testosterone and is often used as a performance-enhancing drug. Hence, it was added to the World Anti-Doping Agency (WADA) prohibited list in 2020.
Aside from illicit consumption, the presence of Clostebol in an athlete's system can also be due to ingestion of contaminated meat or coming into contact with some cream/spray-based medications that are used for skin wounds, abrasions, erosions, fissures, and burns. As per WADA, creams and sprays containing Clostebol are used extensively in Italy. In the USA, Clostebol is a Schedule III controlled substance, which means that it is considered to have potential for abuse as well as medicine.
Several high-profile athletes have faced suspension over Clostebol doping in recent years. San Diego Padres star Fernando Tatis Jr. was suspended from MLB in 2022 after testing positive for the substance. As reported by AP, Tatis Jr. said he accidentally took a medication containing Clostebol to treat ringworm.
Norwegian cross-country skier and four-time Olympic gold medalist, Therese Johaug faced an 18-month suspension in October 2016 after testing positive for the anabolic steroid. As a result, she missed the 2018 Winter Olympics in PyeongChang. Johaug said Clostebol entered her system through a cream she used for her sunburned lips while training in Italy.
Jannik Sinner was inadvertently contaminated with Clostebol
Jannik Sinner tested positive for Clostebol in two urine sample tests on March 10 and 18. A four-year suspension is the standard sanction for a player who has tested positive for a controlled substance. However, Sinner immediately appealed and continued to play on the ATP Tour while an Independent Tribunal was hearing his case.
The Independent Tribunal concluded its investigation and released its report on August 20, ruling that the reigning Australian Open champion bore “no fault or negligence” for both positive tests. During the investigation, it was found that Sinner had been unintentionally contaminated with Clostebol by his physio, Giacomo Naldi.
Naldi had reportedly been using Trofodermin spray containing Clostebol to treat a cut on his finger during the 2024 Indian Wells Masters, where Sinner tested positive for doping. Naldi passed on Clostebol into Sinner's body through a bare-handed body massage.
After two urine tests, Sinner was found to have less than one billionth of a gram of Clostebol in his system, which was deemed non-performance enhancing by the ITIA. Seeing his non-complacency in the events that transpired, the Independent Tribunal exonerated Jannik Sinner.
However, he was not let off without any repercussions. The tribunal ruled that Sinner would lose the $325,000 prize money and 400 rankings points he earned at the Indian Wells Masters, where he reached the semifinals. Sinner recently won his fifth title this year at the 2024 Cincinnati Open and will now head to New York for the US Open.