Trimetazidine’s Recurrent Controversy and Impact in Sports

The substance trimetazidine, also known as TMZ, has once again become a subject of discussion in sports, following the suspension of five-time tennis Grand Slam champion and world number two Iga Swiatek. Her suspension resulted from consuming medication found to be contaminated with TMZ, although this is not the first instance of the drug generating controversy within the athletic community. Trimetazidine is a pharmaceutical agent typically prescribed for cardiac conditions, including angina, which manifests as chest pain due to diminished blood flow to the heart. Its mechanism involves enhancing blood flow to the heart and stimulating glucose metabolism, effects that can boost endurance. Consequently, it is classified as a prohibited substance in elite athletic competitions. The World Anti-Doping Agency (Wada), the global organization responsible for coordinating anti-doping regulations and policies across various sports, maintains an annually updated “List of Prohibited Substances and Methods”. Trimetazidine is categorized on this list as a ‘metabolic modulator’. These types of drugs enhance cardiac efficiency without substantially altering blood pressure or heart rate. Wada enforces a ban on TMZ both during and outside of competition, with detection typically occurring through urine samples. Meldonium, another substance classified as a metabolic modulator, resulted in a 15-month ban from tennis for five-time Grand Slam winner Maria Sharapova after she tested positive for it. Indeed, TMZ has been central to multiple high-profile doping incidents. Earlier this year, Russian figure skater Kamila Valieva received a four-year ban from the Court of Arbitration for Sport, following a positive test for TMZ in a sample obtained prior to her participation in the 2022 Winter Olympics. At the age of 15, Valieva was a member of Russia’s figure skating team, which had initially secured first place in the team event. Subsequent to her doping ban, the International Skating Union (ISU) earlier this year reclassified Russia’s medal from gold to bronze. Kamila Valieva’s positive test for the prohibited heart medication TMZ was recorded in December 2021. In 2021, prior to the Tokyo Olympics, twenty-three Chinese swimmers also registered positive tests for TMZ. They were subsequently permitted to participate in the Games after China’s national anti-doping agency determined that the positive results stemmed from contamination. Wada had previously stated it was “not in a position to disprove the possibility that contamination was the source of TMZ,” but the agency has since initiated a review of these failed tests. It has been observed in numerous instances that athletes inadvertently consume TMZ due to contamination. Valieva asserted that her positive test result might have originated from consuming food prepared on a chopping board her grandfather used to crush his medication. Nevertheless, the Court of Arbitration for Sport stated that it could not substantiate this claim with “any concrete evidence.” Tennis world number two Swiatek’s positive test for TMZ was recorded in a urine sample collected in August 2024. She faced a provisional suspension starting 12 September, but subsequently won an appeal. Swiatek is now cleared to compete again from 4 December 2024. Following an investigation, the International Tennis Integrity Agency (ITIA) concluded that the positive test was attributable to the contamination of melatonin, a regulated non-prescription medication Swiatek was using for jet lag and sleep difficulties.