An urgent review of the use of naltrexone (including implants) for opioid dependence is needed following reports of severe adverse reactions, according to two articles in the latest Medical Journal of Australia.
In its editorial, Associate Professor Robert Ali, Director of the Drug Alcohol Services Council in Adelaide, and his co-authors said that naltrexone is theoretically an attractive treatment for opioid dependence because it is inexpensive, long-acting, and generally well tolerated.
Oral naltrexone is used as a treatment for heroin and alcohol dependence.
However, the effectiveness and safety of oral treatments is compromised by poor patient adherence to taking regular doses. This has led to the development of long-acting naltrexone implants and depot injections.
Naltrexone implants have not been approved for human use in Australia, but these implants are being supplied through some private clinics.
Assoc. Prof. Ali says that naltrexone implants are currently obtained through the TGA Special Access Scheme but without the product being subjected to the usual rigorous scrutiny required for new devices in Australia.
"It is concerning that the recent research on naltrexone implants in Australia has not followed usual scientific processes," he said.
In a related study published in the journal, Dr Paul Haber, Head of Drug Health Services at Royal Prince Alfred Hospital, and his co-authors studied 12 patients who were admitted to hospital soon after receiving naltrexone in oral or implant form.
Eight of the cases were definitely or probably related to the naltrexone implant, including cases of severe opiate withdrawal and dehydration, infection at the implant site requiring surgery, and a psychiatric disorder.
The authors said these severe adverse events challenge the notion that naltrexone implants are a safe procedure.
"These events suggest a need for careful case selection, careful clinical management, and for closer regulatory monitoring to protect this marginalised and vulnerable population," Dr Haber said.
"Patients should be warned of the associated risks, and appropriate procedures planned to respond to any complications."
Dr Haber also emphasises the importance of screening patients for underlying medical or psychiatric conditions and, importantly, coordinating with relevant service providers.
"Similarly, a close relationship between naltrexone implant providers and local emergency departments is important."
"The widespread and unregulated use of naltrexone implants without appropriate safeguards for patients, their families and service providers should be restricted until this therapeutic product has been assessed for safety and effectiveness," he said.
The Medical Journal of Australia is a publication of the Australian Medical Association.