Matthew Mellon, the cryptocurrency billionaire who died suddenly while preparing for rehab in Cancun, had tried to treat his opioid addiction using a hallucinogenic drug banned in the U.S., Page Six reports. Mellon, who had been open about his struggles with OxyContin for years, reportedly tried ibogaine to kick his habit while in Mexico. The psychoactive drug, derived from a root found in Africa, has been banned in the U.S. for decades but is seen as an antidote to addiction in some overseas treatment centers. “Matthew had tried ayahuasca but it did not agree with him, so he moved on to try ibogaine,” an unnamed source was quoted as saying by Page Six. It was not immediately clear if Mellon had taken the drug at a rehabilitation center, but ibogaine is reportedly offered at several facilities in Cancun. A rep for Mellon’s family initially said the billionaire died abruptly in a rehab center but later said he died while planning to check into a treatment program.