Food and Drug Administration officials say the next wave of drug abuse could involve opioid substitutes.

These substitutes include gabapentinoids, loperamide, benzodiazepines, and kratom.

"We must be aware that any decisive actions taken to reduce prescription opioid abuse and stem the tide of overdose and death can have unintended consequences, including prompting people to turn to alternative, potentially dangerous substances," the officials wrote in a recent letter published in The New England Journal of Medicine.

New addiction trends seem to materialize overnight. For the Food and Drug Administration, every drug is a potential suspect.

In a letter published Wednesday in The New England Journal of Medicine, the FDA officials Douglas C. Throckmorton, Scott Gottlieb, and Janet Woodcock warned that non-opioid painkillers could be at the forefront of the next wave of drug abuse.

"We must be aware that any decisive actions taken to reduce prescription opioid abuse and stem the tide of overdose and death can have unintended consequences, including prompting people to turn to alternative, potentially dangerous substances," the officials wrote in the letter.

There were more than 42,000 deaths in the US attributed to opioids in 2016, and 40% of all opioid-overdose deaths involve prescription opioids, according to the Centers for Disease Control and Prevention.

The FDA says it is reducing excess amounts of opioids in circulation, encouraging doctors to prescribe drugs other than opioids when possible, and developing new therapeutics to help people dealing with pain.

But efforts to curb prescription-opioid abuse by the FDA could effectively shift use to opioid substitutes instead.

Substances that the agency is closely watching are gabapentinoids, which are used to treat seizures and neuropathic pain; loperamide, an over-the-counter treatment for diarrhea; benzodiazepines, which are used to treat anxiety; and kratom, a plant-based supplement with psychoactive effects that can enhance mood and offer pain relief.

The FDA says it is able to get at the forefront of the latest trends in drug addiction by sifting through internet forums and online mentions to detect concerning patterns. While opioid substitutes are safe when used appropriately, instances of misuse have attracted the agency's attention.