A variant of the club drug ketamine could be reformulated for use as an antidepressant, a new study suggests. The three-week study found depressed people who took the drug reported improvement.

Ketamine, also known as Special K, is used as a veterinary tranquilizer. Much of the ketamine sold on the street has been diverted from veterinarians’ offices. Ketamine’s chemical structure and mechanism of action are similar to those of PCP. Researchers hope to produce a ketamine-like drug that does not produce side effects such as hallucinations and delusions, HealthDay reports.

The study used a drug called lanicemine, which works in a similar way to ketamine in the brain. The 152 people with depression in the study were randomly assigned to receive either 100 milligrams or 150 milligrams of the drug or a placebo intravenously at three-day intervals over the course of three weeks.

Participants who took the drug were more likely to report improvement in their depression while they received treatment and for several weeks afterwards. Many reported dizziness. They did not report having hallucinations and delusions.

The study is published in Molecular Psychiatry. Lanicemine is thought to affect brain circuits more selectively than ketamine, according to a journal news release.