He had been receiving ketamine infusions for depression and anxiety, but the last infusion was weeks before his death, so this must have been ketamine use on his own given the half-life. It was also an extremely high dose well above ketamine infusion therapy dosage.
Gotta say, as someone who receives ketamine infusions for depression, they don’t give you enough to do any of that. If ketamine killed him, it was because he found some on the street.
On an additional note, this may be a cautionary tale on giving someone ketamine with a predisposition to addiction. It may be in the best interests of ketamine clinics everywhere to do routine drug testing to ensure patient safety, but not as a means of punishment.