From 2014 through 2017, there was an increase in US poison control calls related to the intentional abuse and misuse of tianeptine, an unapproved antidepressant drug, the US Centers for Disease Control and Prevention said in a report on Thursday.

Tianeptine, marketed as Coaxil or Stablon, is used as a prescription antidepressant in Europe, Asia and Latin America. In the US, it can be purchased on the Internet, even though the US Food and Drug Administration has not approved its use.

There have been reports that recreational abuse might result in severe side effects including vomiting, confusion, coma and kidney failure. The drug can be lethal in rare cases.

"Deaths associated with misuse of tianeptine have been reported outside the United States," CDC researchers wrote in the new report. They added that two recent deaths attributed to "tianeptine toxicity" occurred in the US after the drug was purchased online.