President Ferdinand Marcos Jr. on Monday accused his predecessor, President Rodrigo Duterte, of taking fentanyl.

Before departing for Vietnam for a state visit, Marcos said that his predecessor has been taking fentanyl for an extended period of time.

When asked about the accusation of former President Rodrigo Duterte that he was a drug addict, Marcos said “I think it’s the fentanyl.”

“The last time he disclosed this to the public was around 5 or 6 years ago," Marcos told the reporters.

“After such a duration, the impact on one's health is substantial. I hope his medical team is diligently addressing these issues and not neglecting the potential problems that may arise,” he added.

The US National Institute on Drug Abuse defines  fentanyl a powerful synthetic (lab-made) opioid that is FDA-approved to treat severe pain related to surgery or complex pain conditions.

Duterte said in 2016 that he had previously used to take fentanyl, a potent opioid painkiller, because of a spinal injury caused by other motorcycle accidents when he was younger.

According to Duterte, his doctor made him stop using fentanyl on learning he was "abusing the drug" by using more than the prescribed patches.

But Sunday evening, Duterte claimed that Marcos is a drug addict and suggested that he might face a fate similar to his father, Ferdinand Marcos Sr., who was ousted from power in 1986 during the EDSA People Power Revolution.