This article says waves of drug abuse tend to alternate between sedatives, like heroin and the current opioid wave, and stimulants, like cocaine and methamphetamine. Like opioids, people are hard at work in labs trying to create synthetic stimulants. One candidate, which according to this article is already popular in “the Middle East party scene”, is Captagon, which has effects similar to cocaine and can be as cheap as $3 per pill.