Up to 490 athletes may have been taking meldonium during the 2015 European Games in Baku, according to research published in the British Journal of Sports Medicine.
Meldonium was placed on the World Anti-Doping Agency's banned list for 2016 and a number of athletes have already tested positive for it, including tennis star Maria Sharapova.
The research was carried out on behalf of the European Olympic Committees and contributed to WADA's decision to ban the use of meldonium in competitive sport.
The findings were based on information volunteered by athletes and medical teams as well as anti-doping tests given at the European Games last June.
Thirteen medallists were found to have been taking meldonium and the drug was detected in athletes competing in 15 of the 21 sports.