The trial was carried out by the Biotrial clinic for Bial, a company that specializes in clinical trials, and took place in the western city of Rennes, France. Some reports claim the drug contains cannabinoids, the active ingredient in cannabis. However, French officials deny that.

French Minister of Health Marisol Touraine said the drug is meant to work on the body's pain center, according to a report in The Guardian.

Of the six male volunteers who were hospitalized, one man is brain dead, three are suffering a "handicap that could be irreversible" and another has neurological problems. The sixth volunteer shows no symptoms but is being monitored.

The study involved 90 people who took some dosage of the drug. The trial has been stopped and all volunteers have been recalled. The case has been referred to the health branch of the Paris prosecutor's office.

The Associated Press reported Friday that no antidote exists for the drug.