Several major U.S. sports leagues are pushing to add the drug that led to a positive test for Russian tennis star Maria Sharapova to their banned list, but in many cases they will need player approval before they can hit that goal.

Sharapova, who last week revealed she had tested positive for the banned drug meldonium at the Australian Open in January, is facing suspension of up to four years by the International Tennis Federation.

The World Anti-Doping Agency (WADA) added meldonium to its banned substance list on Jan. 1 after concluding it improves blood flow and boosts exercise capacity. Most North American sports groups do not automatically follow WADA’s list, and must in turn negotiate with unionized players to add any drugs to their respective banned lists.

The PGA Tour, the organizer of the main professional golf tours in North America, told Reuters it plans to add meldonium to its banned list, while Major League Baseball (MLB) said it has raised the issue with its players. The National Basketball Association (NBA), National Football League (NFL) and the National Collegiate Athletic Association (NCAA) all said they plan to explore a possible ban.

Only the U.S. Olympic Committee (USOC) and Major League Soccer banned the drug when WADA did.

The PGA Tour generally follows the WADA list with few exceptions, said Andy Levinson, vice president of anti-doping. Golf’s banned list was last revised in October, prior to the start of the 2015-2016 season. “Meldonium will be added in the 2016 revision,” he said.

Athletes who test positive for a banned drug face fines and suspensions. Any players who might argue they need meldonium for medical reasons can still apply for what most sports call a therapeutic-use exemption, which allows athletes who have a doctor’s backing to take a banned substance with league approval.

Some experts said athletes may have a hard time proving their medical need for a drug sold only in a few former Soviet countries and not approved for use in western Europe or the United States.

Meldonium is marketed as Mildronate by the Latvian pharmaceutical firm Grindeks, which has said the drug could protect athletes from cell damage, but would be unlikely to improve their competitive performance.

WADA said last week it had recorded 99 positive tests for the recently-banned drug and according to research in the British Journal of Sports Medicine, use of meldonium was widespread among elite athletes competing at the European Games in Baku last year.

“The sheer prevalence of meldonium indicates that the athletes believe it has performance-enhancing benefits,” said Michael Pearlmutter, executive director of the Partnership for Clean Competition, an anti-doping organization started in 2008 with funding from the USOC, MLB and the NFL.

Baseball said the drug is already banned in its minor leagues, where the sport does not have to negotiate with the players. At the major league level, the sport approached the union about adding meldonium to the banned list after WADA prohibited it but before Sharapova’s positive test became public news.

“We are still in discussions with the MLBPA regarding any additions to the banned list in the Major Leagues for the 2016 season,” MLB spokesman Patrick Courtney said of the players’ union, Major League Baseball Players Association.

The NBA has a prohibited substances committee that includes players’ union members and the league said it will be raising meldonium with the committee.

NFL spokesman Brian McCarthy said the sport’s officials “periodically review the list of prohibited substances with our medical advisors and make modifications as appropriate. ​We anticipate it will be a topic of discussion this offseason.”

NCAA spokesman Christopher Radford said the college sports group’s committee that oversees testing would review the drug’s classification at its next meeting in June. While the committee considers what WADA is doing, it does not automatically adopt the anti-doping group’s banned list, he said.

National Hockey League spokesman Schuyler Baehman said the earliest meldonium could be added to the league’s banned list would be in advance of next season. He declined to say whether the sport would negotiate with the players to ban the drug.