Risk-factors for methadone-specific deaths in Scotland's methadone-prescription clients between 2009 and 2013

Opioid-related deaths and their counterpart by occurrence era, age group and coimplicated drugs: Scotland vs. England and Wales

AIMS

Compare by occurrence era and age group how opioid-related deaths (ORDs) and their counterpart evolved in Scotland vs. England and Wales during 2006-2020. For Scotland, compare coimplication rates between ORDs and non-ORDs for any benzodiazepine, cocaine or gabapentin/pregabalin, and consider whether coimplication in ORDs depended on opioid-specificity.

METHODS

Cross-tabulations of drug misuse deaths (DMDs) obtained by 3 yearly occurrence era (2006-2008 to 2018-2020) and age group (under 25, 25-34, 35-44, 45-54, 55+ years) for England and Wales and subdivided by whether at least 1 opiate was mentioned on death certificate (DMD-Os or not); and of Scotland's opioid-related deaths (ORDs vs. non-ORDs) together with (i) coimplication by any benzodiazepine, cocaine or gabapentin/pregabalin; and (ii) opioid-specificity of ORDs. ORD is defined by heroin/morphine, methadone or buprenorphine being implicated in DMD.

RESULTS

Per era between 2012-2014 and 2018-2020, Scotland's ORDs increased by 54% and non-ORDs by 34%. Increase in DMD-Os in England and Wales was more modest. Cocaine was implicated in 83% of Scotland's 2690 non-ORDs during 2006-2020; and any benzodiazepine in 53% of 8409 ORDs. However, in 2018-2020, coimplication rates in 2926 ORDs (880 non-ORDs) were 81% (33%) for any benzodiazepine, 30% (74%) for cocaine and 38% (22%) for gabapentin/pregabalin. Coimplication rate in 2018-2020 for any benzodiazepine was lowest at 70% (616/877) for heroin/morphine ORDs; and, by age group, at 66% (160/241) for ORDs aged 55+ years.

CONCLUSIONS

Drug testing to inform users, shared intelligence between police and public health for earlier detection of changes in supply and monitoring of prescribed daily-dose of methadone are urgent.

Mortality among individuals prescribed opioid-agonist therapy in Scotland, UK, 2011-20: a national retrospective cohort study

BACKGROUND

Drug-related death (DRD) rate in Scotland, UK, has increased rapidly to one of the highest in the world. Our aim was to examine the extent to which opioid-agonist therapy (OAT) in Scotland is protective against drug-related mortality and how this effect has varied over time.

METHODS

We included individuals in Scotland with opioid use disorder who received at least one OAT prescription between Jan 1, 2011, and Dec 31, 2020. We calculated drug-related mortality rates and used Quasi-Poisson regression models to estimate trends over time and by OAT exposure, adjusting for potential confounding.

FINDINGS

In a cohort of 46 453 individuals prescribed OAT with a total of 304 000 person-years of follow-up, DRD rates more than trebled from 6·36 per 1000 person-years (95% CI 5·73-7·01) in 2011-12 to 21·45 (20·31-22·63) in 2019-20. DRD rates were almost three and a half times higher (hazard ratio 3·37; 95% CI 1·74-6·53) for those off OAT compared with those on OAT after adjustment for confounders. However, confounder adjusted DRD risk increased over time for both people off and on OAT.

INTERPRETATION

Drug-related mortality rates among people with opioid use disorders in Scotland increased between 2011 and 2020. OAT remains protective but is insufficient on its own to slow the increase in DRD risk for people who are opioid dependent in Scotland.

FUNDING

Scottish Government Drug Deaths Taskforce, Public Health Scotland, and National Institute for Health and Care Research.

Cause-Specific Mortality among Patients in Treatment for Opioid Use Disorder in Multiple Settings: A Prospective Comparative Cohort Study

INTRODUCTION

Among people receiving current or previous opioid maintenance treatment (OMT), the leading cause of premature death is an opioid overdose. However, other causes of mortality remain high in this group. An understanding of causes of deaths across multiple settings can be useful in informing more comprehensive prevention responses. The aim of this study was to describe all non-overdose causes of death in three national cohorts (Czechia, Denmark, and Norway) among OMT patients and to explore associations of non-overdose mortality with age and gender.

METHODS

This prospective comparative cohort study used national mortality registry databases for OMT patients from Czechia (2000-2019), Denmark (2000-2018), and Norway (2010-2019). Crude mortality rates and age-standardized mortality rates (ASMRs) were calculated as deaths per 1,000 person years for cause-specific mortality.

RESULTS

In total, 29,486 patients were included, with 5,322 deaths recorded (18%). We found variations in causes of death among the cohorts and within gender and age groups. The leading non-overdose causes of death were accidents in Czechia and Denmark, and neoplasms in Norway. Cardiovascular deaths were highest in Czechia, particularly for women in OMT (ASMR 3.59 vs. 1.24 in Norway and 1.87 in Denmark).

CONCLUSION

This study found high rates of preventable death among both genders and all age groups. Different demographic structures, variations in risk exposure, as well as variations in coding practices can explain the differences. The findings support increased efforts towards screening and preventative health initiatives among OMT patients specific to the demographic characteristics in different settings.

Undetected Respiratory Depression in People with Opioid Use Disorder

BACKGROUND

Opioid-related deaths are increasing globally. Respiratory complications of opioid use and underlying respiratory disease in people with Opioid Use Disorder (OUD) are potential contributory factors. Individual variation in susceptibility to overdose is, however, incompletely understood. This study investigated the prevalence of respiratory depression (RD) in OUD treatment and compared this to patients with chronic obstructive pulmonary disease (COPD) of equivalent severity. We also explored the contribution of opioid agonist treatment (OAT) dosage, and type, to the prevalence of RD.

METHODS

There were four groups of participants: 1) OUD plus COPD ('OUD-COPD', n = 13); 2) OUD without COPD ('OUD', n = 7); 3) opioid-naïve COPD patients ('COPD'n = 13); 4) healthy controls ('HC'n = 7). Physiological indices, including pulse oximetry (SpO₂%), end-tidal CO₂ (ETCO₂), transcutaneous CO₂ (TcCO₂), respiratory airflow and second intercostal space parasternal muscle electromyography (EMG_para), were recorded continuously over 40 min whilst awake at rest. Significant RD was defined as: SpO₂%< 90% for > 10 s, ETCO₂ per breath > 6.6 kPa, TcCO₂ overall mean > 6 kPa, respiratory pauses > 10 s RESULTS: At least one indicator was observed in every participant with OUD (n = 20). This compared to RD episode occurrence in only 2/7 HC and 2/13 COPD participants (p < 0.05,Fisher's exact test). The occurrence of RD was similar in OUD participants prescribed methadone (n = 6) compared to those prescribed buprenorphine (n = 12).

CONCLUSIONS

Undetected RD is common in OUD cohorts receiving OAT and is significantly more severe than in opioid-naïve controls. RD can be assessed using simple objective measures. Further studies are required to determine the association between RD and overdose risk.

Identifying the changing age distribution of opioid-related mortality with high-frequency data

Background

Opioid-related mortality continues to rise across North America, and mortality rates have been further exacerbated by the COVID-19 pandemic. This study sought to provide an updated picture of trends of opioid-related mortality for Ontario, Canada between January 2003 and December 2020, in relation to age and sex.

Methods

Using mortality data from the Office of the Chief Coroner for Ontario, we applied Bayesian Poisson regression to model age/sex mortality per 100,000 person-years, including random walks to flexibly capture age and time effects. Models were also used to explore how trends might continue into 2022, considering both pre- and post-COVID-19 courses.

Results

From 2003 to 2020, there were 11,633 opioid-related deaths in Ontario. A shift in the age distribution of mortality was observed, with the greatest mortality rates now among younger individuals. In 2003, mortality rates reached maximums at 5.5 deaths per 100,000 person-years (95% credible interval: 4.0–7.6) for males around age 44 and 2.2 deaths per 100,000 person-years (95% CI: 1.5–3.2) for females around age 51. As of 2020, rates have reached maximums at 67.2 deaths per 100,000 person-years (95% CI: 55.3–81.5) for males around age 35 and 16.8 deaths per 100,000 person-years (95% CI: 12.8–22.0) for females around age 37. Our models estimate that opioid-related mortality among the younger population will continue to grow, and that current conditions could lead to male mortality rates that are more than quadruple those of pre-pandemic estimations.

Conclusions

This analysis may inform a refocusing of public health strategy for reducing rising rates of opioid-related mortality, including effectively reaching both older and younger males, as well as young females, with health and social supports such as treatment and harm reduction measures.

Why are drug-related deaths among women increasing in Scotland? A mixed-methods analysis of possible explanations

Drug-related deaths have increased significantly in Scotland in recent years, with a much greater percentage increase in deaths among women than among men. We undertook a mixed-methods project to identify explanations for this trend, comprising three parallel methodological strands: (i) an analysis of available routine data, including drug treatment data, death registrations, and surveys of people using needle exchanges; (ii) thematic analysis of interviews and focus groups with professional stakeholders and (iii) secondary analysis of interviews with women who use drugs. Results indicated that the observed trend is likely to reflect multiple, interacting causes. Potential contributors identified were: ageing; changing patterns of substance use; increasing prevalence of physical and mental health co-morbidities; changing relationships and parenting roles; changes to treatment services and wider health and social care provision; unintended consequences or poor implementation of recovery-oriented practice; and changes in the social security system. Policy responses to rising drug-related death rates require a gender-informed approach, recognising the commonalities and differences between men and women who use drugs; the diversity of experiences within each gender; and the intersections between gender and other forms of inequality, such as poverty.

Mechanisms and context in the San Patrignano drug recovery community, Italy: a qualitative study to inform transfer to Scotland

The San Patrignano drug recovery community, Italy, is regarded as one of the most successful in the world. However, if this model is to be transferred to other countries, it is necessary to clarify its underlying mechanisms and how far their success is context dependent. This qualitative study investigated these features of the San Patrignano model. Data collection included semi-structured interviews with six key stakeholders and 10 days’ observational field notes. Data were synthesised using frameworks and analysis was informed by realist principles. Individual level mechanisms include: commitment to change, removal from former social environment, communal living, peer mentor with lived experience and meaningful work. These operate in the context of a free of charge, long term (3–4 year) residential community. Organisational level mechanisms are: visionary leadership, staff dedication, social enterprise and adaptable learning. Organisational contextual factors include: a gap in suitable provision for drug recovery and the region’s high level of social capital. Articulating the programme theory of the recovery model and its contextual dependency helps clarify which elements should be transferred and how far they need to be adapted for different socio-cultural settings. The recognition of context is crucial when considering transfer of effective complex interventions across countries.

Increasing drug-related mortality rates over the last decade in Scotland are not just due to an ageing cohort: A retrospective longitudinal cohort study

BACKGROUND

In Europe, North America, and Australia, mortality due to drug-related (DR) causes amongst people who inject drugs (PWID) is a major issue. Our objective was to characterise temporal trends in DR mortality rates in a large cohort of PWID in Scotland over the past decade, all of whom had been diagnosed with hepatitis C virus (HCV) infection, and to investigate factors associated with DR mortality.

METHODS

Retrospective longitudinal cohort study linking Scotland's national HCV Diagnosis Database and deaths registry. The study cohort consisted of all individuals with likely injection drug use-related route of HCV acquisition, who had been diagnosed with HCV between 1991 and 2018, and were alive and aged under 65 years on 1 January 2009. We used Lexis expansion to adjust for ageing cohort effects and calculated the mortality rate from an underlying/contributing DR cause over the period 2009-2018. We fitted Poisson regression models to estimate the temporal trend adjusting for attained age, sex, referral setting, region, and viraemic status at baseline.

RESULTS

Amongst the study population (n = 35,065; 236,914 person-years), a total of 1900 DR deaths occurred; the DR mortality rate increased from 5.6/1000 [101 deaths] in 2009 to 12.4/1000 [342] person-years in 2018. Increasing trends were observed for all age-groups except 55-64 years. The overall DR mortality rate was highest for referrals for HCV testing from prison (11.0/1000) and hospital settings (10.0/1000). Mortality increased with calendar time period, with significantly raised adjusted rate ratios (RRs) from 2015 (RR=1.40, 95% CI:1.16-1.69) to 2018 (RR=2.23, 95% CI:1.88-2.64), compared with 2011-2012, for older age (35-44: RR=1.37, 95% CI:1.20-1.56; 45-54: RR=1.32, CI:1.14-1.53) compared with <35 years, for persons diagnosed with HCV since 2009 (RR=1.34, 95% CI:1.21-1.49), and for prison and hospital referrals (RRs of 1.30, 1.37) compared with GP referrals.

CONCLUSION

Increasing DR mortality rates in Scotland over the past decade are not just due to an ageing cohort. Harm reduction services will likely need to expand and adapt to reverse the recent upward trends in DR mortality in PWID.

Drug fatalities and treatment fatalism: Complicating the ageing cohort theory

Deaths related to drug 'misuse' remain at an all-time high in the United Kingdom (UK). Older heroin consumers are particularly at risk, with the highest rates of deaths among people aged 40-49 and the steepest rises in the over-fifty age bracket. Accordingly, a popular theory for the UK's increase in drug-related deaths, made by the government, and propelled in the media, is that there is an ageing cohort of heroin users with age-related health complications predisposing them to an overdose. However, drawing on in-depth interviews with those people deemed to be most at risk, this article works to complicate this theory, with participants citing a shift in (a) experience and responsibility, (b) route of administration, (c) desired effects, (d) acceptance of their drug use and 'user' status and (e) valuing health. Disrupting age as a given risk factor, this article turns attention away from the individual and these 'natural' processes to what participants describe as a singular, punitive, and inflexible treatment system and its intersecting structures. Approaching life and death as a matter of sociomaterial 'mattering', this article rethinks a reductionist, causal link between age and drug-related death with a treatment despondency and fatalism that could prove fatal.

Troponin, A Predictor of Mortality in Methadone Exposure: An Observational Prospective Study

Background

Methadone poisoning/overdose is a global public health problem. We aimed to determine whether methadone poisoning increased cardiac troponin and whether high‐sensitivity cardiac troponin I (hs‐cTnI) levels predicted the need for intensive care unit admission, intubation, and mortality.

Methods and Results

This observational, prospective single‐center study was done at Loghman‐Hakim Hospital (Tehran, Iran) from June 2018 until February 2019. Patients aged >14 years admitted with a diagnosis of methadone exposure were included. Patients were excluded if they had coexisting conditions associated with elevated hs‐cTnI levels. An ECG and hs‐cTnI levels were obtained on emergency department presentation. Patients were followed up on their need for intubation, intensive care unit admission, and in‐hospital mortality. Of 245 included patients (186 [75.9%] men; median age, 33 years), most referred to loss of consciousness (210 cases, 89%). Nineteen (7.7%) patients had hs‐cTnI levels of >0.1 ng/mL (positive), and 41 (16.7%) had borderline levels of 0.019 to 0.1 ng/mL. Twenty‐three (9.3%) cases were admitted to the intensive care unit, 21 (8.5%) needed intubation, and 5 (2%) died during hospitalization. An hs‐cTnI cutoff value of 0.019 ng/mL independently predicted mortality. For optimal concomitant sensitivity and specificity, receiver operating characteristic curve analysis was conducted and showed that hs‐cTnI had an independent significant association with mortality, with a cutoff value of 0.0365 ng/mL (odds ratio, 38.1; 95% CI, 2.3–641.9; P<0.001).

Conclusions

Methadone exposure/toxicity is a newly identified cause of elevated hs‐cTnI. Values >0.019 ng/mL, and particularly >0.0365 ng/mL, of hs‐cTnI predicted mortality in our sample. Future studies should measure troponin levels in methadone maintenance treatment clients to assess the risk of myocardial injury from long‐term exposure.

The Role of Risk or Contributory Death Factors in Methadone-Related Fatalities: A Review and Pooled Analysis

Methadone-related deaths are characterized by a wide range of post-mortem blood concentrations, due to the high pharmacokinetic/dynamic inter-individual variability, the potential subjective tolerance state and to other risk factors or comorbidities, which might enhance methadone acute toxicity. In the present study, the association among pre-existing and external conditions and diseases and the resultant methadone death capacity have been investigated. Beside a systematic literature review, a retrospective case-control study was done, dividing cases in which methadone was the only cause of death (controls), and those with associated clinical-circumstantial (naive/non-tolerant state), pathological (pulmonary or cardiovascular diseases) or toxicological (other drugs detected) conditions. Methadone concentrations were compared between the two groups and the association with conditions/diseases was assessed by multiple linear and binomial logistic regressions. Literature cases were 139, in house 35, consisting of 22 controls and 152 cases with associated conditions/diseases. Mean methadone concentrations were 2122 ng/mL and 715 ng/mL in controls and cases respectively, with a statistically significant difference (p < 0.05). Lower methadone concentrations (by 24, 19 and 33% respectively) were detected in association with naive/non-tolerant state, pulmonary diseases and presence of other drugs, and low levels of methadone (<600 ng/mL) might lead to death in the presence of the above conditions/diseases.

Scotland's 2009-2015 methadone-prescription cohort: Quintiles for daily dose of prescribed methadone and risk of methadone-specific death

AIMS

As methadone clients age, their drug-related death (DRD) risks increase, more than doubling at 45+ years for methadone-specific DRDs.

METHODS

Using Community Health Index (CHI) numbers, mortality to 31 December 2015 was ascertained for 36 347 methadone-prescription clients in Scotland during 2009-2015. Cohort entry, quantity of prescribed methadone and daily dose (actual or recovered by effective, simple rules) were defined by clients' first CHI-identified methadone prescription after 30 June 2009 and used in proportional hazards analysis. As custodian of death records, National Records of Scotland identified non-DRDs from DRDs. Methadone-specific DRD means methadone was implicated but neither heroin nor buprenorphine.

RESULTS

The cohort's 192 928 person-years included 1857 non-DRDs and 1323 DRDs (42%), 546 of which were methadone specific. Actual/recovered daily dose was available for 26 533 (73%) clients who experienced 420 methadone-specific DRDs. Top quintile for daily dose at first CHI-identified methadone prescription was >90 mg. Age 45+ years at cohort-entry (hazard ratio vs 25-34 years: 3.1, 95% confidence interval: 2.4-4.2), top quintile for baseline daily dose of prescribed methadone (vs 50-70 mg: 1.9, 1.1-3.1) and being female (1.3, 1.0-1.6) significantly increased clients' risk of methadone-specific DRD.

CONCLUSION

Extra care is needed when methadone daily dose exceeds 90 mg. Females' higher risk for methadone-specific DRD is new and needs validation. Further analyses of prescribed daily dose linked to mortality for large cohorts of methadone clients are needed internationally, together with greater pharmacodynamic and pharmacokinetic understanding of methadone by age and sex. Balancing age-related risks is challenging for prescribers who manage chronic opiate dependency against additional uncertainty about the nature, strength and pharmacological characteristics of drugs from illegal markets.

Fatal accident inquiries into 83 deaths in Scottish prison custody: 2010-2013

BACKGROUND

The only non-legal reference in Lord Cullen's Review of fatal accident inquiry (FAI) Legislation in Scotland (2009) was my audit of FAIs into 97 deaths in prison custody in Scotland, 1999-2003: recommending that waiting time from prisoner death to end of FAI should be less than 1 year for 90% of FAIs, and epidemiological rules for FAIs to have a written determination versus formal findings.

AIMS

Audit of FAIs into 83 deaths in Scottish prison custody in the period 2010-2013.

METHOD

Assessement of waiting times from prisoner death to end of FAI; dissemination of written determinations; self-inflicted death rate per 1000 prisoner-years; cause of natural deaths; and yellow card submissions. Detailed cross-checking was nec37essary between Scottish Prison Service and courts' websites and the Scottish Fatalities Investigation Unit.

RESULTS

Of 83 FAIs into deaths in Scottish prison custody, 2010-2013, 37 (45%) were long-awaited (ongoing >2 years after the prisoner's death); 16 (19%, 95% CI 11-28%) beyond 3 years. Of 37 long-awaited FAIs, 27 made written determinations but only 12 of these (44%) were published. Self-inflicted deaths numbered 36: 1.1 per 1000 prisoner-years (95% CI 0.75-1.48). Of 47 deaths from natural causes, cardiovascular disease accounted for 23 (49%, 95% CI 34-63%); liver disease was implicated in 10 of 47. To support pharmacovigilance, submissions were made to Medicines and Healthcare Regulatory Agency for eight deaths (10%, 95% CI 4-19%).

CONCLUSIONS

FAIs into prisoner deaths in Scotland are too long-awaited given that four (5%) identified precautions that could have prevented death.

Improving prescribing through big data approaches-Ten years of the Scottish Prescribing Information System

Medicines are a major component of modern healthcare delivery, both in resource consumption and as drivers of innovation. The ever-increasing application of digitalisation within day-to-day living and as part of our healthcare systems-with the resultant data generation-presents the opportunity to better define the populations exposed to medicines, and their benefits and harm in real world settings. This article outlines the development of the Scottish National Prescribing Information System (PIS) and describes how this capability is being used to support the safe and effective use of medicines, both nationally and internationally. Since 2009, PIS has included e-prescribed/e-dispensed and reimbursed medicines data, now totalling 976 million prescriptions, with codified structured data on dose instructions. A literature review, covering the period from January 2009 to March 2019, identified 40 full publications using PIS, the first occurring in 2014. The majority involved pharmacoepidemiology/drug-use studies (50%) in cancer and cardiovascular disease. Measuring the value and impact of PIS was extended beyond publication quantification by illustrating the translation of PIS outputs into the learning health system at scale. The developing Scottish capabilities add breadth and depth to the wider evolving international environment, and offer the potential to contribute collegiately to the global effort on medicine safety and effectiveness, including support for the World Health Organisation Global Patient Safety Challenge: Medication Without Harm.

COPD and asthma in patients with opioid dependency: a cross-sectional study in primary care

Patients treated for drug addiction have high asthma and COPD prevalence rates. The relative contributions of cigarette smoking, smoking intensity and possible smoking of other substances has not been described. We aimed to describe the prevalence and determinants of asthma and COPD in patients prescribed methadone as opioid substitution therapy (OST). In a cross-sectional study of an anonymised patient-level primary care dataset of UK inner-city general practices (n = 46), 321,395 patients aged ≥18 years were identified. A total of 676 (0.21%) had a record of a methadone ever issued in primary care. The association between respiratory disease and methadone prescribing was examined using logistic regression. Models were adjusted for potential effects of clustering by practice. A total of 97.3% of patients prescribed methadone were cigarette smokers, either current (81.2%) or ex-smokers (16.1%). The prevalences of asthma and COPD were higher in methadone patients (14.2% and 12.4%, respectively) compared to non-methadone patients (4.4% and 1.1%, respectively). Methadone was an independent determinant of asthma, adjusting for smoking status (OR 3.21; 95% CI: 2.52, 4.10) or for smoking intensity (3.08; 2.27, 4.19), and of COPD, adjusting for smoking status (6.00; 4.61, 7.80) or for smoking intensity (5.80; 4.12, 8.17). COPD and asthma prevalence were substantially higher in those prescribed methadone compared to those never prescribed methadone. Prescription of methadone was an independent predictor for both COPD and asthma, even after adjustment for smoking status and smoking intensity. Possible explanations include confounding by association with smoking of heroin or crack cocaine, both of which may have a causal association with COPD and asthma.

MultiBUGS: A Parallel Implementation of the BUGS Modelling Framework for Faster Bayesian Inference

MultiBUGS is a new version of the general-purpose Bayesian modelling software BUGS that implements a generic algorithm for parallelising Markov chain Monte Carlo (MCMC) algorithms to speed up posterior inference of Bayesian models. The algorithm parallelises evaluation of the product-form likelihoods formed when a parameter has many children in the directed acyclic graph (DAG) representation; and parallelises sampling of conditionally-independent sets of parameters. A heuristic algorithm is used to decide which approach to use for each parameter and to apportion computation across computational cores. This enables MultiBUGS to automatically parallelise the broad range of statistical models that can be fitted using BUGS-language software, making the dramatic speed-ups of modern multi-core computing accessible to applied statisticians, without requiring any experience of parallel programming. We demonstrate the use of MultiBUGS on simulated data designed to mimic a hierarchical e-health linked-data study of methadone prescriptions including 425,112 observations and 20,426 random effects. Posterior inference for the e-health model takes several hours in existing software, but MultiBUGS can perform inference in only 28 minutes using 48 computational cores.

Evaluating the population impact of hepatitis C direct acting antiviral treatment as prevention for people who inject drugs (EPIToPe) - a natural experiment (protocol)

INTRODUCTION

Hepatitis C virus (HCV) is the second largest contributor to liver disease in the UK, with injecting drug use as the main risk factor among the estimated 200 000 people currently infected. Despite effective prevention interventions, chronic HCV prevalence remains around 40% among people who inject drugs (PWID). New direct-acting antiviral (DAA) HCV therapies combine high cure rates (>90%) and short treatment duration (8 to 12 weeks). Theoretical mathematical modelling evidence suggests HCV treatment scale-up can prevent transmission and substantially reduce HCV prevalence/incidence among PWID. Our primary aim is to generate empirical evidence on the effectiveness of HCV 'Treatment as Prevention' (TasP) in PWID.

METHODS AND ANALYSIS

We plan to establish a natural experiment with Tayside, Scotland, as a single intervention site where HCV care pathways are being expanded (including specialist drug treatment clinics, needle and syringe programmes (NSPs), pharmacies and prison) and HCV treatment for PWID is being rapidly scaled-up. Other sites in Scotland and England will act as potential controls. Over 2 years from 2017/2018, at least 500 PWID will be treated in Tayside, which simulation studies project will reduce chronic HCV prevalence among PWID by 62% (from 26% to 10%) and HCV incidence will fall by approximately 2/3 (from 4.2 per 100 person-years (p100py) to 1.4 p100py). Treatment response and re-infection rates will be monitored. We will conduct focus groups and interviews with service providers and patients that accept and decline treatment to identify barriers and facilitators in implementing TasP. We will conduct longitudinal interviews with up to 40 PWID to assess whether successful HCV treatment alters their perspectives on and engagement with drug treatment and recovery. Trained peer researchers will be involved in data collection and dissemination. The primary outcome - chronic HCV prevalence in PWID - is measured using information from the Needle Exchange Surveillance Initiative survey in Scotland and the Unlinked Anonymous Monitoring Programme in England, conducted at least four times before and three times during and after the intervention. We will adapt Bayesian synthetic control methods (specifically the Causal Impact Method) to generate the cumulative impact of the intervention on chronic HCV prevalence and incidence. We will use a dynamic HCV transmission and economic model to evaluate the cost-effectiveness of the HCV TasP intervention, and to estimate the contribution of the scale-up in HCV treatment to observe changes in HCV prevalence. Through the qualitative data we will systematically explore key mechanisms of TasP real world implementation from provider and patient perspectives to develop a manual for scaling up HCV treatment in other settings. We will compare qualitative accounts of drug treatment and recovery with a 'virtual cohort' of PWID linking information on HCV treatment with Scottish Drug treatment databases to test whether DAA treatment improves drug treatment outcomes.

ETHICS AND DISSEMINATION

Extending HCV community care pathways is covered by ethics (ERADICATE C, ISRCTN27564683, Super DOT C Trial clinicaltrials.gov: NCT02706223). Ethical approval for extra data collection from patients including health utilities and qualitative interviews has been granted (REC ref: 18/ES/0128) and ISCRCTN registration has been completed (ISRCTN72038467). Our findings will have direct National Health Service and patient relevance; informing prioritisation given to early HCV treatment for PWID. We will present findings to practitioners and policymakers, and support design of an evaluation of HCV TasP in England.

Mortality and causes of death among patients with opioid use disorder receiving opioid agonist treatment: a national register study

BACKGROUND

Mortality rates and causes of death among individuals in opioid agonist treatment (OAT) vary according to several factors such as geographical region, age, gender, subpopulations, drug culture and OAT status. Patients in OAT are ageing due to effective OAT as well as demographic changes, which has implications for morbidity and mortality. Norway has one of the oldest OAT populations in Europe. Because of the varying mortality rates and causes of death in different subgroups and countries, research gaps still exist. The aims of this study were to describe the causes of death among OAT patients in Norway, to estimate all-cause and cause-specific crude mortality rates (CMRs) during OAT and to explore characteristics associated with drug-induced cause of death compared with other causes of death during OAT.

METHODS

This was a national, observational register study. Data from the Norwegian Cause of Death Registry and the Norwegian Patient Registry were combined with data from medical records. We included all patients in the Norwegian OAT programme who died not more than 5 days after the last intake of OAT medication, between 1 January 2014 and 31 December 2015.

RESULTS

In the 2-year observation period, 200 (1.4%) of the OAT patients died. A forensic or medical autopsy was performed in 63% of the cases. The mean age at the time of death was 48.9 years (standard deviation 8.4), and 74% were men. Somatic disease was the most common cause of death (45%), followed by drug-induced death (42%), and violent death (12%). In general, CMRs increased with age, and they were higher in men and in patients taking methadone compared with buprenorphine. Increasing somatic comorbidity, measured by the Charlson comorbidity index, reduced the odds of dying of a drug-induced cause of death compared with other causes of death.

CONCLUSIONS

Both somatic and drug-induced causes of death were common during OAT. Improved treatment and follow-up of chronic diseases, especially in patients aged > 40 years, and continuous measures to reduce drug-induced deaths appear to be essential to reduce future morbidity and mortality burdens in this population.

Electrocardiographic Findings in Mortalities Due to Pure Methadone Toxicity

We aimed to evaluate electrocardiographic (ECG) abnormalities in mortalities due to pure methadone toxicity in ICU patients since methadone-related mortality may be due to cardiac complications even in acute toxicities. In a retrospective single-center study, files of all patients who had died with confirmed diagnosis of pure methadone toxicity between 2011 and 2016 were evaluated. Autopsy was performed in all cases. A cardiologist measured all ECG quantitative and qualitative indices. Fifty-one deaths were recorded. Forty-two dead patients were males. Median [IQR] age of the patients was 44 [30, 60] years. Of them, 38 (69%) were methadone-dependent and were significantly older than methadone-naïve patients (p = 0.008 and p = 0.001, respectively). ECG abnormalities were detected in all cases. ST-T abnormalities were found in 33 (64.7%) patients. Except longer PR interval in dependent patients (p = 0.017) and specific ST elevation in naïve cases (p = 0.008), other ECG indices were similar in two groups. No correlation was found between ST-T abnormalities and coronary disease in autopsy. ECG abnormalities irrelevant to coronary artery diseases are common in methadone-related mortalities. Methadone toxicity may affect myocardium and play a role in death. Further prospective studies to evaluate other cardiac indices in methadone-poisoned patients are recommended.

Non drug-related and opioid-specific causes of 3262 deaths in Scotland's methadone-prescription clients, 2009-2015

BACKGROUND

Opioid drug use is a major cause of premature mortality, with opioid substitution therapy the leading intervention. As methadone-clients age, non-drug-related deaths (non-DRDs) predominate and DRD-risks increase differentially, quadrupling at 45+ years for methadone-specific DRDs.

METHODS

36,606 methadone-prescription-clients in Scotland during 2009-2015 were linked to mortality records to end-2015 by their Community Health Index (CHI). Cohort-entry, also baseline quantity of prescribed methadone, were defined by clients' first CHI-identified methadone-prescription during 2009-2015. National Records of Scotland identified non-DRDs from DRDs; and provided ICD10 codes for underlying and co-present causes of death. Methadone-specific DRD means methadone was implicated in DRD but neither heroin nor buprenorphine.

RESULTS

During 193,800 person-years of follow-up, 1939 non-DRDs (59%) and 1323 DRDs occurred, of which 546 were methadone-specific. Predominant underlying ICD10 chapters for non-DRDs were: neoplasm (377); external causes (341); diseases of digestive (303), circulatory (286) or respiratory (212) system. As methadone-clients aged, the non-DRD proportion of their deaths increased from 54% (717/1318) at 35-44 years to 89% (372/417) at 55+ years. After allowing for DRDs' opioid-specificity, age-group and quintile for last-prescribed methadone, there was a significant, positive interaction for co-present circulatory disease between top-quintile for prescribed methadone and 45+ years at death (p = 0.033 after Bonferroni); not for digestive or respiratory co-presence.

CONCLUSIONS

Circulatory disease is the co-morbidity most likely implicated in the quadrupling of methadone-specific DRD-risk at 45+ years; followed by digestive disease. Cultural shift is needed in treatment-services because degenerative non-DRDs predominate as methadone-clients age. Future linkage-studies should access hospitalizations and methadone-daily-dose.

Use of text-mining methods to improve efficiency in the calculation of drug exposure to support pharmacoepidemiology studies

Background

Efficient generation of structured dose instructions that enable researchers to calculate drug exposure is central to pharmacoepidemiology studies. Our aim was to design and test an algorithm to codify dose instructions, applied to the NHS Scotland Prescribing Information System (PIS) that records about 100 million prescriptions per annum.

Methods

A natural language processing (NLP) algorithm was developed that enabled free-text dose instructions to be represented by three attributes - quantity, frequency and qualifier - specified by three, three and two variables, respectively. A sample of 15 593 distinct dose instructions was used to test, validate and refine the algorithm. The final algorithm used a zero-assumption approach and was then applied to the full dataset.

Results

The initial algorithm generated structured output for 13 152 (84.34%) of the 15 593 sample dose instructions, and reviewers identified 767 (5.83%) incorrect translations, giving an accuracy of 94.17%. Following subsequent refinement of the algorithm rules, application to the full dataset of 458 227 687 prescriptions (99.67% had dose instructions represented by 4 964 083 distinct instructions) generated a structured output for 92.3% of dose instruction texts. This varied by therapeutic area (from 86.7% for the central nervous system to 96.8% for the cardiovascular system).

Conclusions

We created an NLP algorithm, operational at scale, to produce structured output that gives data users maximum flexibility to formulate, test and apply their own assumptions according to the medicines under investigation. Text mining approaches can provide a solution to the safe and efficient management and provisioning of large volumes of data generated through our health systems.

The impact of buprenorphine and methadone on mortality: a primary care cohort study in the United Kingdom

AIMS

To estimate whether opioid substitution treatment (OST) with buprenorphine or methadone is associated with a greater reduction in the risk of all-cause mortality (ACM) and opioid drug-related poisoning (DRP) mortality.

DESIGN

Cohort study with linkage between clinical records from Clinical Practice Research Datalink and mortality register.

SETTING

UK primary care.

PARTICIPANTS

A total of 11 033 opioid-dependent patients who received OST from 1998 to 2014, followed-up for 30 410 person-years.

MEASUREMENTS

Exposure to methadone (17 373, 61%) OST episodes or buprenorphine (9173, 39%) OST episodes. ACM was available for all patients; information on cause of death and DRP was available for 5935 patients (54%) followed-up for 16 363 person-years. Poisson regression modelled mortality by treatment period with an interaction between OST type and treatment period (first 4 weeks on OST, rest of time off OST, first 4 weeks off OST, rest of time out of OST censored at 12 months) to test whether ACM or DRP differed between methadone and buprenorphine. Inverse probability weights were included to adjust for confounding and balance characteristics of patients prescribed methadone or buprenorphine.

FINDINGS

ACM and DRP rates were 1.93 and 0.53 per 100 person-years, respectively. DRP was elevated during the first 4 weeks of OST [incidence rate ratio (IRR) = 1.93 95% confidence interval (CI) = 0.97-3.82], the first 4 weeks off OST (IRR = 8.15, 95% CI = 5.45-12.19) and the rest of time out of OST (IRR = 2.13, 95% CI = 1.47-3.09) compared with mortality risk from 4 weeks to end of treatment. Patients on buprenorphine compared with methadone had lower ACM rates in each treatment period. After adjustment, there was evidence of a lower DRP risk for patients on buprenorphine compared with methadone at treatment initiation (IRR = 0.08, 95% CI = 0.01-0.48) and rest of time on treatment (IRR = 0.37, 95% CI = 0.17-0.79). Treatment duration (mean and median) was shorter on buprenorphine than methadone (173 and 40 versus 363 and 111, respectively). Model estimates suggest that there was a low probability that methadone or buprenorphine reduced the number of DRP in the population: 28 and 21%, respectively.

CONCLUSIONS

In UK general medical practice, opioid substitution treatment with buprenorphine is associated with a lower risk of all-cause and drug-related poisoning mortality than methadone. In the population, buprenorphine is unlikely to give greater overall protection because of the relatively shorter duration of treatment.

Distribution of take-home opioid antagonist kits during a synthetic opioid epidemic in British Columbia, Canada: a modelling study

BACKGROUND

Illicit use of high-potency synthetic opioids has become a global issue over the past decade. This misuse is particularly pronounced in British Columbia, Canada, where a rapid increase in availability of fentanyl and other synthetic opioids in the local illicit drug supply during 2016 led to a substantial increase in overdoses and deaths. In response, distribution of take-home naloxone (THN) overdose prevention kits was scaled up (6·4-fold increase) throughout the province. The aim of this study was to estimate the impact of the THN programme in terms of the number of deaths averted over the study period.

METHODS

We estimated the impact of THN kits on the ongoing epidemic among people who use illicit opioids in British Columbia and explored counterfactual scenarios for the provincial response. A Markov chain model was constructed explicitly including opioid-related deaths, fentanyl-related deaths, ambulance-attended overdoses, and uses of THN kits. The model was calibrated in a Bayesian framework incorporating population data between Jan 1, 2012, and Oct 31, 2016.

FINDINGS

22 499 ambulance-attended overdoses and 2121 illicit drug-related deaths (677 [32%] deaths related to fentanyl) were recorded in the study period, mostly since January, 2016. In the same period, 19 074 THN kits were distributed. We estimate that 298 deaths (95% credible interval [CrI] 91-474) were averted by the THN programme. Of these deaths, 226 (95% CrI 125-340) were averted in 2016, following a rapid scale-up in distribution of kits. We infer a rapid increase in fentanyl adulterant at the beginning of 2016, with an estimated 2·3 times (95% CrI 2·0-2·9) increase from 2015 to 2016. Counterfactual modelling indicated that an earlier scale-up of the programme would have averted an additional 118 deaths (95% CrI 64-207). Our model also indicated that the increase in deaths could parsimoniously be explained through a change in the fentanyl-related overdose rate alone.

INTERPRETATION

The THN programme substantially reduced the number of overdose deaths during a period of rapid increase in the number of illicit drug overdoses due to fentanyl in British Columbia. However, earlier adoption and distribution of the THN intervention might have had an even greater impact on overdose deaths. Our findings show the value of a fast and effective response at the start of a synthetic opioid epidemic. We also believe that multiple interventions are needed to achieve an optimal impact.

FUNDING

Canadian Institutes of Health Research Partnerships for Health Systems Improvement programme (grant 318068) and Natural Science and Engineering Research Council of Canada (grant 04611).

Ageing opioid users' increased risk of methadone-specific death in the UK

BACKGROUND

The first evidence that the hazard ratio (HR) for methadone-specific death rises more steeply with age-group than for all drug-related deaths (DRDs) came from Scotland's cohort of 33,000 methadone-prescription clients. We aim to examine, for England, whether illicit opioid users' risk of methadone-specific death increases with age; and to pool age-related HRs for methadone-specific deaths with those for Scotland's methadone-prescription clients.

METHODS

The setting is all services in England that provide publicly-funded, structured treatment for illicit opioid users, the methodology linkage of the English National Drug Treatment Monitoring System and mortality database, and key measurements are DRDs, methadone-specific DRDs, or heroin-specific DRDs, by age-group and gender, with proportional hazards adjustment for substances used, injecting status and periods in/out of treatment.

RESULTS

Linkage was achieved for 129,979 adults receiving prescribing treatment modalities for opioid dependence during April 2005 to March 2009 and followed-up for 378,009 person-years (pys). There were 1,266 DRDs: 271 methadone-specific (7 per 10,000 pys: irrespective of gender) and 473 heroin-specific (15 per 10,000 pys for males, 7 for females). Methadone-specific DRD-rate per 10,000 person-years was 3.5 (95% CI: 2.7-4.4) at 18-34 years, 8.9 (CI: 7.3-10.5) at 35-44 years and 18 (CI: 13.8-21.2) at 45+ years; heroin-specific DRD-rate was unchanged with age. Relative to 25-34 years, pooled HRs for UK clients' methadone-specific deaths were: 0.87 at <25 years (95% CI: 0.56-1.35); 2.14 at 35-44 years (95% CI: 1.76-2.60); 3.75 at 45+ years (95% CI: 2.99-4.70).

CONCLUSION

International testing and explanation are needed of UK's sharp age-related increase in the risk of methadone-specific death. Clients should be alerted that their risk of methadone-specific death increases as they age.

Multiple Systems Estimation (or Capture-Recapture Estimation) to Inform Public Policy

Estimating population sizes has long been of interest, from the estimation of the human or ecological population size within regions or countries to the hidden number of civilian casualties in a war. Total enumeration of the population, for example, via a census, is often infeasible or simply impractical. However, a series of partial enumerations or observations of the population is often possible. This has led to the ideas of capture-recapture methods, which have been extensively used within ecology to estimate the size of wildlife populations, with an associated measure of uncertainty, and are most effectively applied when there are multiple capture occasions. Capture-recapture ideology can be more widely applied to multiple data-sources, by the linkage of individuals across the multiple lists. This is often referred to as Multiple Systems Estimation (MSE). The MSE approach has been preferred when estimating "capture-shy" or hard-to-reach populations, including those caught up in the criminal justice system; or homeless; or trafficked; or civilian casualties of war. Motivated by a range of public policy applications of MSE, each briefly introduced, we discuss practical problems with potentially substantial methodological implications. They include: "period" definition; "case" definition; when an observed count is not a true count of the population of interest but an upper bound due to mismatched definitions; exact or probabilistic matching of "cases" across different lists; demographic or other information about the "case" which may influence capture-propensities; required permissions to access extant-lists; list-creation by research-teams or interested parties; referrals (if presence on list A results - almost surely - in presence on list B); different mathematical models leading to widely different estimated population sizes; uncertainty in estimation; computational efficiency; external validation; hypothesis-generation; and additional independent external information. Returning to our motivational applications, we focus on whether the uncertainty which qualified their estimates was sufficiently narrow to orient public policy; and, if not, what options were available and/or taken to reduce the uncertainty or to seek external validation. We also consider whether MSE was hypothesis-generating: in the sense of having spawned new lines of inquiry.

Suspected Methadone Toxicity: from Hospital to Autopsy Bed

High mortality rates have been reported for methadone in both adults and children. We aimed to determine the pattern of toxicity, possible underlying diseases and treatment challenges in patients referred to our centre with early diagnosis of methadone toxicity and who later died. Medical files of all methadone-poisoned patients who had been admitted to a referral centre of toxicology between March 2011 and March 2016, died during the hospital stay and sent for autopsy to Legal Medicine Organization were retrospectively evaluated. In a total of 94 patients, autopsy findings and laboratory evaluations showed that cause of death was pure methadone toxicity in 57 (60.6%). Other causes of death were ischaemic heart disease in ten, co-ingestions (toxicities including methadone) in eight, brain haemorrhage, multi-organ failure and pneumosepsis (each in four), meningitis/encephalitis in three and head trauma and other toxicities (other than methadone but including an opioid, each in two) patients. Time of cardiopulmonary arrest was significantly different between those with pure methadone toxicity and those who died due to other causes (p = 0.01). Patients who had died due to co-ingestions and other toxicities were younger (p = 0.029) and took more bolus doses of naloxone (p = 0.042). In methadone users, especially in older ages and those with trivial response to naloxone administration, loss of consciousness should not be strictly attributed to methadone toxicity. In such patients, thorough evaluation for other possible causes of loss of consciousness is mandatory.