Some people who practice Asian traditional medicine consider kratom to be a substitute for opium.
https://www.fundable.com/stella-kratom
 
Our findings revealed that, although in vitro studies have found kratom preparations’ most abundant alkaloid—mitragynine—to cause a prolonged QTc interval and an increased risk of torsades de pointes, a clinical study examining humans’ regular consumption of kratom did not report such a risk.