Made infamous as the club drug “Special K,” ketamine is now considered a wonder drug for some people with hard-to-treat depression. An inhaled version of the drug has been approved for severe depression. Many clinics, however, are now offering injections or infusions of ketamine for a range of mental health conditions.

According to NBC News, ketamine is a hallucinogen that has been approved by the Food and Drug Administration as an anesthetic for decades, but has also been used illegally as a party drug. Growing research has found that ketamine also works for treatment-resistant depression in some people. The FDA then gave its approval to a version of the drug called esketamine, or Spravato, in 2019. It’s an inhaled version that must be administered in a doctor’s office, and its approved only for people for whom other treatments failed.

Over the years, a new industry has emerged. Clinics are offering ketamine off-label either as an infusion or an injection for a wide variety of mental health problems. NBC News explains that “off label” use means the drug hasn’t been specifically approved for those conditions.

One example is Field Trips, a national chain of clinics that’s offered ketamine-assisted therapy for several mental health conditions since 2019. After a screening process, patients can get shots of ketamine as they lounge in comfort wearing eye masks, while clinicians lead them through a guided meditation. The patients meet with therapists before and after their “trips.”

“Patients say, ‘This changed my life,’” said Mike Dow, a psychotherapist at a Field Trip clinic in Los Angeles. Dow believes the drug works by boosting feel-good chemicals like traditional antidepressants, reducing inflammation, and forming new neural pathways to create new habits and behaviors. He adds that some patients experience psychedelic experience that also boost their mood.

But some experts worry that the mushrooming of these clinics across the country could be dangerous. They aren’t federally regulated, but are subject to state laws similar to other outpatient clinics.

“The concern with these clinics popping up is that people are getting treatments that haven’t been well-proven, well-studied or following any guidelines,” said Dr. Smita Das, who is board certified in psychiatry, addiction psychiatry and addiction medicine and is an associate professor at Stanford University School of Medicine. “My concern is that people who need treatment will spend their money and energy in these ketamine clinics that aren’t well-proven.”