WASHINGTON (AP) — The decades-old surgical drug ketamine has found a new use — as an alternative to opioids for patients with chronic pain.

Ketamine is now being prescribed as a psychedelic therapy for an array of unapproved uses, including depression and anxiety.

Behind the trend are investors setting up for-profit ketamine clinics, as well as online prescribing services that send the drug through the mail.

There is limited evidence that it’s effective for arthritis, migraines and other forms of pain.

Some experts worry the U.S. may be repeating the mistakes that gave rise to the opioid crisis by overprescribing an unproven drug with safety and abuse risks.