[Naltrexone implants--a pilot project]

Abstract

Background: An increasing number of Norwegian heroin addicts have had naltrexone implants abroad without proper documentation. The authors established a joint project to study duration and safety.

Material and methods: Methodology to measure naltrexone in plasma was developed. 10 patients had 21 implants. Plasma samples were collected before, one and three hours after implantation, daily for one week, then weekly. Patient satisfaction, side effects and unwanted medical events were recorded.

Results: Patients had a protective level of naltrexone for 35-80 days. Side effects were few. Two patients had abstinence reactions caused by insufficient detoxification. Two patients had their repeat implants removed because of tissue reactions. One patient developed hepatitis C infection in the second week after implantation. One had transient increase in transaminases after heavy multi-drug use. The others were without signs of hepatic toxicity.

Interpretation: Use of implants secures a prolonged period of naltrexone protection. Implants are mostly well tolerated, but tissue reactions to repeat implants could be a problem. Evaluation of the patients should be thorough and the treatment integrated in a competent follow up.