Year-long opiate substitution for drug misusers has 85 percent chance of cutting deaths

Researchers from Bristol and London found that the length of time people had opiate substitution treatment (OST) for had a large impact on its success and the likelihood of death.

Opiate users have a high risk of death, often from overdose.

OST, mostly methadone and buprenorphine, is central to prevention of drug related mortality and often delivered in primary care settings. Over the past 10 years, opiate prescription has more than doubled while the number of deaths involving methadone has fallen. However, the overall number of opiate deaths has not decreased and targets to reduce overdose deaths in England and Wales have not been met.

Previous research has shown that there may be an elevated risk of death during OST initiation (first 28 days) and in the first few weeks after OST has been stopped.

So the researchers studied data from the General Practice Research Database (GPRD), a database containing anonymised patient records from more than 460 general practices in the UK.

They analysed data on 5,577 patients who had a substance abuse diagnosis and received 267,003 OST prescriptions during 1990-2005. These patients were followed up until one year after the expiry of their last OST prescription, or the date of death before this time has passed, or the date of transfer away from the practice.

The researchers looked at mortality rates comparing periods in and out of treatment compared with the general population.

A total of 178 (3%) patients died either on treatment or within a year of their last prescription. The rate of death amongst people off treatment was almost double that of people taking treatment.

In the first two weeks of OST, the mortality rate was 1.7 per 100 person years -- more than three times higher than the mortality rate during the rest of time on treatment.

The mortality rate was also raised substantially in the period immediately after treatment and people were eight to nine times more likely to die in the month immediately after stopping OST.

The researchers calculated that OST had an 85% and higher chance of reducing overall mortality in opiate users if they were taking the treatment for 12 months or longer.

They conclude: "Clinicians and patients should be aware of the increased mortality risk at the start of opiate substitution treatment and immediately after stopping treatment. Further research is needed to investigate the effect of average duration of opiate substitution treatment on drug related mortality."