Experts say naltrexone implants for drug dependency are risky

Apr 20 2008

Experts in Australia say the use of naltrexone implants to treat drug dependency should be stopped because of a number of reports of severe adverse reactions.

Naltrexone is used orally as a treatment for heroin and alcohol dependence but only works if it is taken regularly.

Because many addicts do not stick to the regular doses prescribed the effectiveness of the drug is often compromised.

This has led to the development of long-acting naltrexone implants and depot injections which have not been approved for human use in Australia, but are being supplied through private clinics.

The implants are usually inserted into the abdominal wall and release the drug over several months.

Associate Professor Robert Ali, Director of the Drug Alcohol Services Council in Adelaide, and his co-authors in research published in the Medical Journal of Australia, says that naltrexone is in theory an attractive treatment because it is inexpensive, long-acting, and generally well tolerated.

Professor Ali says he is concerned that naltrexone implants are currently obtained through the TGA Special Access Scheme even though the product has not undergone the usual rigorous scrutiny required for new devices in Australia.

Professor Ali says that the recent research on naltrexone implants in Australia has not followed usual scientific processes and his concern has the support of others in the field.

Dr. Paul Haber, Head of Drug Health Services at Royal Prince Alfred Hospital studied 12 patients who were admitted to hospital soon after receiving naltrexone in oral or implant form.

Dr. Haber says of the 12 cases, 8 were either definitely or probably related to the naltrexone implant; these included cases of severe opiate withdrawal and dehydration, infection at the implant site requiring surgery, and a psychiatric disorder.

Dr. Haber says such severe adverse events challenge the notion that naltrexone implants are a safe procedure and says there is a need for careful case selection, careful clinical management, and for closer regulatory monitoring.

He says patients should be warned of the risks, and appropriate procedures planned to respond to any complications.

Dr. Haber also believes screening patients for underlying medical or psychiatric conditions is essential along with working with relevant service providers and emergency services until the product has been assessed for safety and effectiveness.

Both studies are published in the Medical Journal of Australia, a publication of the Australian Medical Association.