Mexico City:  Mexican president-elect Andres Manuel Lopez Obrador may consider the idea of selling opium for pharmaceutical use, a senior aide said on Wednesday, a sign of the deep changes the next government is considering in the war on drugs.

"Why not sell it to pharmaceutical companies?" said Olga Sanchez, a former Supreme Court judge who is the incoming president's pick to run the Interior Ministry.

She said Obrador, a 64-year-old former mayor of Mexico City, supported a public consultation on the possibility of regulating opium and decriminalising marijuana.

Obrador did not take a clear stance on decriminalising drugs before Sunday's election, but said he would try out new approaches to tackling Mexico's violence, including possible amnesty for some cartel employees.

The United States has been engulfed by an epidemic of opioid addiction in recent years that has led to tens of thousands of overdose deaths. The Drug Enforcement Administration says 93 per cent of the heroin on US streets is produced in Mexico.

In Mexico, the battle for control of heroin production and trafficking is held partly responsible for the country's record violence, which led to nearly 30,000 murders last year.