Marijuana is to be taken off Major League Baseball's banned substances list, the governing body has announced.
The policy, which comes into effect in 2020, says players found to have taken natural cannabinoids will be treated the same as alcohol-related issues.
All samples will now also be tested for opioids, fentanyl, cocaine and synthetic THC.
Players who test positive for these substances will be referred for treatment before possible discipline.
"The USA opioid epidemic is a concern," MLB deputy chief Dan Halem said.
"It is our hope that this agreement - which is based on principles of prevention, treatment, awareness and education - will help protect the health and safety of our players.
"It is our collective hope that this agreement will help raise public awareness on the risks and dangers of opioid medications and contribute positively to a national conversation about this important topic."
The revised policy comes months after the death of Los Angeles Angels pitcher Tyler Skaggs, 27, whose autopsy showed oxycodone, fentanyl and alcohol in his system.