HEROIN addicts may one day be treated with a polymer implant instead of taking a daily dose of the heroin substitute methadone. Researchers at Johns Hopkins School of Medicine in Baltimore have developed a button-sized implant that releases a steady stream of hydromorphone for up to three months (Journal of Substance Abuse Treatment, vol 14, p 535). Hydromorphone, like methadone, blocks opiate receptors in the brain that bind to heroin, eliminating cravings and withdrawal symptoms. Heroin addicts have to take a dose every of methadone day---and increasingly they are being forced to travel to clinics to prevent the growth of an underground trade in the drug. The implanted polymer releases a steady stream of hydromorphone, which is as effective at blocking opiate receptors as methadone, over one to three months.

The implant should increase the number of people successfully completing heroin therapy. "The primary reason for patients wanting to get out of methadone treatment is the inconvenience," says George Bigelow, director of the behavioural pharmacology research division at Johns Hopkins. The implant will also cut the cost of treating addicts. This is between $3500 and $4500 a year, though methadone makes up only 7 per cent of the total.

However, the researchers do not recommend the implant for people who need counselling, such as those beginning treatment. Counselling is often coupled with the daily dose of the substitute drug, and such addicts might relapse without it.

Heroin addicts may have to wait several years for the implant. The researchers are first considering using the implant to relieve the pain of cancer before they study it in heroin addicts.

Kate 0'Rourke, Baltimore