Mr Walker "stumbled" across kratom at a social gathering when he was introduced to a kratom advocate who gave him some of the product.

He does not deny the efficacy of the pharmaceuticals he was on but said he could not tolerate the "fogginess" in his mental processes that narcotics produced.

For the past four years, he has used kratom twice a day in powdered form as a shot with chocolate milk or orange juice.

He has been able to give up almost all of his prescriptions and experiences no withdrawal or side effects from discontinued use of kratom.

What next for kratom users?

Kratom users now find themselves in limbo. A new Trump Administration may mean months of vetting and confirming new officials who will have a say in the decision about kratom’s availability in the marketplace - including a new Attorney General and his subordinate DEA chief.

But for millions of Americans who claim that they have escaped opioids by means of this member of the coffee family, the decisive issue may be plain: if kratom cannot be proven to hurt people then why shouldn't Americans be able to use it?