BEIJING (Reuters) – China has imposed new restrictions on the opioid oxycodone, its drug regulator said, as the country tightens control of its painkillers industry in the battle against drug addiction.

Oxycodone, among the heavy-duty painkillers blamed for the deadly opioid crisis in the United States, will be classified as a pyschotropic drug in some formulations and require more approvals to produce or prescribe them, the National Medical Products Administration said late on Tuesday.

Oral solid formulations with more than 5 mg of oxycodone per unit will be categorized as first-class psychotropic drugs from Sept. 1, the agency said.

Formulations with less than 5 mg of oxycodone per unit, as well as composite oral solid formulations with buprenorphine and naloxone, will be categorized as second-class psychotropic drugs at the same time, it said.

Under current laws, first class pyschotropic drugs are banned from sale to retail customers, and second class products cannot be sold to minors.

The laws also require state approvals for pharmaceutical firms to use first-class psychotropic drugs as active ingredients in their products, and hospitals can only purchase these products from suppliers designated by authorities.

Chinese media have voiced concern over oxycodone addiction in the country. Financial magazine Caixin reporting in March that opioid users accounted for 38.1% of the 2.5 million people who were known to have abused drugs in China in 2016.

Liu Xiaodong, a professor at China Pharmaceutical University, said the tighter controls would help to reduce the illegal use of oxycodone.

“Many medicines are useful, but abusing them would turn them into (illicit) drugs,” Liu told Reuters.

Narcotics produced in China have become a contentious issue in relations with the United States.

This month, President Donald Trump accused his Chinese counterpart Xi Jinping of failing to meet promises to stop the flow of the synthetic opioid fentanyl into the United States.

(Reporting by Roxanne Liu and Brenda Goh; editing by Darren Schuettler)