The Food and Drug Administration on Tuesday recommended classifying 7-OH, a compound with opioid-like effects found in unregulated tablets, gummies and drink mixes sold in gas stations and convenience stores, as an illicit substance. Such a move by the Justice Department would restrict or prohibit access to the products, which are also currently sold online. The chemical, formally known as 7-hydroxymitragynine, is often marketed as a way to help people relax, relieve pain or improve their mood or focus. But studies suggest it’s more potent than morphine, and the FDA has warned it could damage the heart or liver and...