How repeated overdoses injure the brain — and why a monthly shot could change that

Every minute between an overdose and resuscitation is a minute closer to brain injury. The survivors who walk away may not realize the damage already done — and repeated episodes compound the harm in ways addiction treatment has largely ignored.

Dr. Nathaniel Day, chief scientific officer at the Canadian Centre of Recovery Excellence (CoRE) under Alberta's Ministry of Mental Health and Addiction, is sounding an alarm that has gone largely unheard in the overdose crisis response: people can survive an overdose and still be left with lasting brain injury.

"Repeated episodes of oxygen deprivation can affect memory, judgment, impulse control, and executive function — the very abilities that people need to navigate treatment and recovery," Day said in a letter published this week in the journal Addiction, co-authored with Dr. Daniel Vigo, the B.C. premier's chief scientific advisor for psychiatry, toxic drugs & concurrent disorders.

The numbers are worrying. In B.C., within a year of a first overdose, between six and ten per cent of those individuals show up in the healthcare system with a brain injury severe enough to be formally diagnosed. But Day points to a deeper problem: small injuries from single overdoses may not trigger immediate diagnosis. "You can be injuring the brain in such a small way that there's no brain injury immediately that's diagnosable. But when you do that 10 times or you do that 20 times, eventually, we may end up with a chronic injury that is serious, but it wasn't enough to diagnose it immediately in the event."

The cascade of injuries appears to be permanent. "If we have somebody who's repeatedly overdosing and they're having stacking events of injury, we would anticipate that for most of those people, there's not going to be a huge recovery in their capacity over time," Day said. "Those injuries accumulate and, in many cases, will be permanent."

Day, an addiction medicine specialist with a medical degree from the University of Alberta and a previous role as provincial medical director of addictions for Alberta Health Services, sees a solution in Sublocade — a long-acting injectable buprenorphine administered once a month. Unlike daily buprenorphine programs common in some private treatment settings, a single monthly dose reduces the gaps where relapse and overdose can occur.

"It allowed a person to continue breathing even though they were overdosing on fentanyl," Day said of one case he documented.

Alberta's Virtual Opioid Dependency Program, available for free the same day a person needs it, is already integrating Sublocade into its offerings. But addiction care has focused heavily on preventing death, Day and his co-authors argue, while overlooking protection of the brain from injury or treatment adaptation for those already living with cognitive impairment from past overdoses.

The person suffering from brain injuries from overdose may not even be aware of it. They may not grasp that help is available. Recovery Alberta announced a $30-million plan in July that includes compassionate intervention and involuntary retention — though the full details of those provisions remain unclear.

What remains unanswered: Alberta's brain-injury rates in the year following a first overdose compared to B.C.'s six to ten per cent, enrollment numbers for the Virtual Opioid Dependency Program, and current prescription figures for Sublocade in the province.