Gibson 2007: overdose deaths with naltrexone implants in place

What they tested

The researchers searched Australian coronial records, the files kept on deaths investigated by a coroner, for deaths between 2000 and 2004 that involved implantable naltrexone. An implant is a pellet placed under the skin that releases naltrexone slowly.

What they found

One man died from acute narcotism, meaning opioid poisoning, while he had a naltrexone implant in place. His blood naltrexone level was 0.3 mg/L, higher than levels reported to block opioids.

A woman died of a combined drug effect that included naltrexone. She also had severe pain at the implant site.

The authors' point was that an implant does not guarantee protection: people can still die of an opioid overdose with one in place.

Limits

• It describes five deaths, and the abstract gives details on only two of them. It can't say how often this happens among people with implants.
• Coroners' records show what happened, not why, so the report can't explain how the overdose got past the blockade.
• The deaths were in Australia between 2000 and 2004, with the implant products available there at that time.

What it means if you're considering naltrexone

Naltrexone blocks opioids, but this report shows the block can be overcome. For someone with opioid use disorder thinking about any form of naltrexone, it's a reminder that taking large amounts of opioids on top of it can still kill.

No naltrexone implant is FDA-approved. The long-acting form approved in the US is Vivitrol, a monthly shot.