Lintzeris 2008: hospital admissions after naltrexone implants in Sydney

What they tested

Researchers went back through hospital files at two Sydney teaching hospitals for patients referred to their drug and alcohol consultation services over 12 months, from August 2006 to July 2007. They recorded each patient's diagnosis, treatment and length of stay.

Naltrexone implants were described as an unlicensed product used in Australia to treat heroin dependence. They were often given along with rapid detoxification, a fast withdrawal from opioids.

What they found

Of the 12 cases, eight were definitely or probably related to the implant or the rapid detox. Six had severe opiate withdrawal with dehydration, staying 2.3 days on average.

One patient had an infection at the implant site, and one had an underlying anxiety disorder that needed psychiatric admission.

Three patients had complications with pain relief, and one had a heart rhythm problem unrelated to the implant.

The authors wrote that these severe adverse events challenge the idea that implants are a safe procedure, and called for careful choice of patients, careful clinical management and closer regulatory monitoring.

Limits

• It counts only cases referred to the consultation services at two hospitals, so it can't say how common these problems are among everyone who has an implant.
• It looked back at existing records, which may leave out details.
• Several problems came from the rapid detox done alongside the implant, not from naltrexone itself.

What it means if you're considering naltrexone

For people considering an implant for opioid use disorder, this audit shows the procedure can send people to hospital, mostly because of severe withdrawal. Naltrexone needs the body to be free of opioids first, and doing that quickly carries its own risks.

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