Risk of death during and after opiate substitution treatment in primary care: prospective observational study in UK General Practice Research Database

Rosie Cornish, John Macleod, John Strang, Peter Vickerman, Matt Hickman, Rosie Cornish, John Macleod, John Strang, Peter Vickerman, Matt Hickman

Abstract

Objective: To investigate the effect of opiate substitution treatment at the beginning and end of treatment and according to duration of treatment.

Design: Prospective cohort study. Setting UK General Practice Research Database.

Participants: Primary care patients with a diagnosis of substance misuse prescribed methadone or buprenorphine during 1990-2005. 5577 patients with 267 003 prescriptions for opiate substitution treatment followed-up (17 732 years) until one year after the expiry of their last prescription, the date of death before this time had elapsed, or the date of transfer away from the practice.

Main outcome measures: Mortality rates and rate ratios comparing periods in and out of treatment adjusted for sex, age, calendar year, and comorbidity; standardised mortality ratios comparing opiate users' mortality with general population mortality rates.

Results: Crude mortality rates were 0.7 per 100 person years on opiate substitution treatment and 1.3 per 100 person years off treatment; standardised mortality ratios were 5.3 (95% confidence interval 4.0 to 6.8) on treatment and 10.9 (9.0 to 13.1) off treatment. Men using opiates had approximately twice the risk of death of women (morality rate ratio 2.0, 1.4 to 2.9). In the first two weeks of opiate substitution treatment the crude mortality rate was 1.7 per 100 person years: 3.1 (1.5 to 6.6) times higher (after adjustment for sex, age group, calendar period, and comorbidity) than the rate during the rest of time on treatment. The crude mortality rate was 4.8 per 100 person years in weeks 1-2 after treatment stopped, 4.3 in weeks 3-4, and 0.95 during the rest of time off treatment: 9 (5.4 to 14.9), 8 (4.7 to 13.7), and 1.9 (1.3 to 2.8) times higher than the baseline risk of mortality during treatment. Opiate substitution treatment has a greater than 85% chance of reducing overall mortality among opiate users if the average duration approaches or exceeds 12 months.

Conclusions: 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.

Conflict of interest statement

Competing interests: None declared.

Figures

https://www.ncbi.nlm.nih.gov/pmc/articles/instance/4787860/bin/corr778340.f1_default.jpg
Fig 1 Adjusted risk of death, compared with not being on treatment, during and after opiate substitution treatment
https://www.ncbi.nlm.nih.gov/pmc/articles/instance/4787860/bin/corr778340.f2_default.jpg
Fig 2 Comparison of risk of death in patients exposed or not exposed to opiate substitution treatment (OST) by duration of treatment. Boxes are interquartile ranges (with median); lines are 95% confidence intervals
https://www.ncbi.nlm.nih.gov/pmc/articles/instance/4787860/bin/corr778340.f3_default.jpg
Fig 3 Probability that opiate substitution treatment (OST) reduces overall mortality for different durations of treatment

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