Do interruptions to the continuity of methadone maintenance treatment in specialist addiction settings increase the risk of drug-related poisoning deaths? A retrospective cohort study

Trends in polysubstance use among patients in methadone maintenance treatment in Ireland: Evidence from urine drug testing 2010-2020

INTRODUCTION

The benefits of methadone maintenance treatment (MMT) may be compromised by the continued use of other substances during treatment. Polysubstance use has been identified as a major contributing factor to treatment discontinuation, a known risk factor for drug overdose. We examined trends in immunoassay drug positivity rates for amphetamines, benzodiazepines, cannabis, cocaine and opioids, and (2) trends in polysubstance positivity rates for drug combinations associated with increased risk of drug overdose among patients attending the national drug treatment centre in Ireland for MMT between 2010 and 2020.

METHODS

Repeated cross-sectional study of patients attending the national drug treatment centre (NDTC) for MMT (total N = 1942) between 2010 and 2020, focused on urine drug samples provided for testing to the NDTC clinical testing laboratory (n = 221,564). Samples were analysed using immunoassay during the study period. Mixed-effects logistic regression models evaluate time trends in drug positivity. A random intercept accounts for repeat testing of individual patients. The study reports Adjusted Odds Ratios (AOR) for time (per year) with 95 % Confidence Intervals (95 % CI).

RESULTS

Drug positivity rates increased over time for benzodiazepines (AOR 1.02, 95 % CI 1.01-1.03, p < .0001), cannabis (AOR 1.06, 95 % CI 1.05-1.08, p < .0001) and cocaine (AOR 1.28, 95 % CI 1.27-1.29, p < .0001), with decreasing trends for opioids (AOR 0.91, 95 % CI 0.91-0.92, p < .0001). Methadone and benzodiazepines were co-detected in over two-thirds of all samples during the study period. Co-detection of methadone and benzodiazepines with cocaine was also found to be increasing (AOR 1.24, 95 % CI 1.23-1.25, p < .0001), with weighted polysubstance positivity rates reaching 29.2 % in 2020. The co-detection of methadone and benzodiazepines with opioids decreased over the study period (AOR 0.92, 95 % CI 0.91-0.92, p < .0001), ranging from 36.7 % in 2010 to 26.9 % in 2020.

CONCLUSION

Interventions are needed to target the persistently high use of benzodiazepines among patients in receipt of methadone due to their synergistic effects with opioids on respiratory depression, enhancing the risk of overdose. The growing use of cocaine among people in MMT also needs to be addressed.

Piloting a Hospital-Based Rapid Methadone Initiation Protocol for Fentanyl

OBJECTIVES

Treating acute opioid withdrawal and offering medications for opioid use disorder (OUD) is critical. Hospitalization offers a unique opportunity to rapidly initiate methadone for OUD; however, little clinical guidance exists. This report describes our experience during the first 9 months following introduction of a hospital-based rapid methadone initiation protocol.

METHODS

We conducted a retrospective chart review of hospitalized patients with OUD seen by our interprofessional addiction medicine consult service at an urban academic center between December 2022 and August 2023. We identified patients who initiated methadone using the rapid methadone initiation protocol, which includes dose recommendations (maximum 60 mg day 1, 70 mg day 2, 80 mg day 3, 100 mg days 4-7) and strict inclusion and exclusion criteria (end organ failure, arrhythmia, concurrent benzodiazepine or alcohol use, age >65).

RESULTS

There were 171 patients that received methadone for OUD during the study period. Of those, 25 patients (15%) received rapid methadone initiation. The average total daily dose of methadone on days 1-7 was 53.0 mg, 69.2 mg, 75.4 mg, 79.5 mg, 87.1 mg, 92.2 mg, and 96.6 mg, respectively. There were no adverse events requiring holding a dose of scheduled methadone, naloxone administration, or transfer to higher level of care.

CONCLUSIONS

A rapid methadone initiation protocol for OUD can be implemented in the inpatient setting. Patients up-titrated their methadone doses quicker than with traditional induction methods, and there were no serious adverse events. Appropriate patient selection may be important to avoid harms.

An international comparative policy analysis of opioid use disorder treatment in primary care across nine high-income jurisdictions

BACKGROUND

Opioid use disorder (OUD) and opioid-related harms are current health priorities in many high-income countries such as Canada. Opioid agonist therapy (OAT) is an effective evidence-based treatment for OUD, but access is often limited.

AIMS

To describe and compare OUD treatment policies across nine international jurisdictions, and to understand how they are situated within their primary care and health systems.

METHODS

Using policy documents, we collected data on health systems, drug use epidemiology, drug policies, and OUD treatment from Australia, Canada, France, Germany, Ireland, Portugal, Sweden, Switzerland, and Taiwan. We used the health system dynamics framework and adapted definitions of low- and high-threshold treatment to describe and compare OUD treatment policies, and to understand how they may be shaped by their health systems context.

RESULTS

Broad similarities across jurisdictions included the OAT pharmacological agents used and the need for supervised dosing; however, preferred OAT, treatment settings, primary care and specialist physicians' roles, and funding varied. Most jurisdictions had elements of lower-threshold treatment access, such as the availability of treatment through primary care and multiple OAT options, but the higher-threshold criteria of supervised dosing.

CONCLUSIONS

From the Canadian perspective, there are opportunities to improve accessibility of OUD care by drawing on how different jurisdictions incorporate multidisciplinary care, regulate OAT medications, remunerate healthcare professionals, and provide funding for services.

Prescription drugs with potential for misuse in Irish prisons: analysis of national prison prescribing trends, by gender and history of opioid use disorder, 2012 to 2020

BACKGROUND

Pharmacotherapy is essential for the delivery of an equivalent standard of care in prison. Prescribing can be challenging due to the complex health needs of prisoners and the risk of misuse of prescription drugs. This study examines prescribing trends for drugs with potential for misuse (opioids, benzodiazepines, Z-drugs, and gabapentinoids) in Irish prisons and whether trends vary by gender and history of opioid use disorder (OUD).

METHODS

A repeated cross-sectional study between 2012 and 2020 using electronic prescribing records from the Irish Prison Services, covering all prisons in the Republic of Ireland was carried out. Prescribing rates per 1,000 prison population were calculated. Negative binomial (presenting adjusted rate ratios (ARR) per year and 95% confidence intervals) and joinpoint regressions were used to estimate time trends adjusting for gender, and for gender specific analyses of prescribing trends over time by history of OUD.

RESULTS

A total of 10,371 individuals were prescribed opioid agonist treatment (OAT), opioids, benzodiazepines, Z-drugs or gabapentinoids during study period. History of OUD was higher in women, with a median rate of 597 per 1,000 female prisoners, compared to 161 per 1,000 male prisoners. Prescribing time trends, adjusted for gender, showed prescribing rates decreased over time for prescription opioids (ARR 0.82, 95% CI 0.80-0.85), benzodiazepines (ARR 0.99, 95% CI 0.98-0.999), Z-drugs (ARR 0.90, 95% CI 0.88-0.92), but increased for gabapentinoids (ARR 1.07, 95% CI 1.05-1.08). However, prescribing rates declined for each drug class between 2019 and 2020. Women were significantly more likely to be prescribed benzodiazepines, Z-drugs and gabapentinoids relative to men. Gender-specific analyses found that men with OUD, relative to men without, were more likely to be prescribed benzodiazepines (ARR 1.49, 95% CI 1.41-1.58), Z-drugs (ARR 10.09, 95% CI 9.0-11.31), gabapentinoids (ARR 2.81, 95% CI 2.66-2.97). For women, history of OUD was associated with reduced gabapentinoid prescribing (ARR 0.33, 95% CI 0.28-0.39).

CONCLUSIONS

While the observed reductions in prescription opioid, benzodiazepine and Z-drug prescribing is consistent with guidance for safe prescribing in prisons, the increase in gabapentinoid (primarily pregabalin) prescribing and the high level of prescribing to women is concerning. Our findings suggest targeted interventions may be needed to address prescribing in women, and men with a history of OUD.

Cost-effectiveness of flexible take-home buprenorphine-naloxone versus methadone for treatment of prescription-type opioid use disorder

BACKGROUND

Our objective was to examine the cost-effectiveness of flexible take-home buprenorphine-naloxone (BNX) versus methadone alongside the OPTIMA trial in Canada.

METHODS

The OPTIMA study was a pragmatic, open-label, noninferiority, two-arm randomized controlled trial, to assess the comparative effectiveness of flexible take-home BNX vs. methadone in routine clinical care for individuals with prescription-type opioid use disorder. We evaluated cost-effectiveness using a semi-Markov cohort model. Probabilities of overdose were calibrated, accounting for fentanyl prevalence and other overdose risk factors such as naloxone availability. We considered health sector and societal cost perspectives, including costs (2020 CAD) for treatment, health resource use, criminal activity, and health state-specific preference weights as outcomes to calculate incremental cost-effectiveness ratios. Six-month and lifetime (3% annual discount rate) time-horizons were explored.

RESULTS

Over a lifetime time horizon, individuals accumulated -0.144 [CI: -0.302, -0.025] incremental quality-adjusted life years (QALYs) in BNX compared with methadone. Incremental costs were -$2047 [CI: -$39,197, $24,250] from a societal perspective, and -$4549 [CI: -$6332, -$3001] from a health sector perspective. Over a six-month time-horizon, individuals accumulated 0.002 [credible interval (CI): -0.011, 0.016] incremental QALYs in BNX compared with methadone. Incremental costs were -$307 [CI: -$10,385, $8466] from a societal perspective and -$1111 [CI: -$1517, -$631] from a health sector perspective. BNX was dominated (costlier, less effective) in 49.7% of simulations when adopting a societal perspective over a lifetime time horizon.

CONCLUSIONS

Flexible take-home BNX was not cost-effective versus methadone over a lifetime time horizon, resulting from better treatment retention in methadone compared to BNX.

Impact of changes to the delivery of opioid agonist treatment, introduced during the COVID-19 pandemic, on treatment access and dropout in Ireland: An interrupted time series analysis

BACKGROUND

Following the emergence of COVID-19, Ireland introduces national contingency guidelines to ensure rapid and uninterrupted access to opioid agonist treatment (OAT). This study aims to assess the impact of changes introduced to the delivery of OAT on the number of people accessing treatment and treatment dropout.

METHODS

The study conducted interrupted time series analyses, with separate segmented regression models (March 2019-February 2020) vs (April 2020-March 2021), for (1) total number of people accessing OAT, (2) the number initiating treatment, and (3) the number dropping out of treatment, using data from the National OAT treatment register. The study examined immediate (change in level or intercept: β₂) and long-term impacts (change in slope; i.e., the difference between the slope before and after the intervention: β₃). We performed total and stratified analyses by gender, age group (<40/≥40 years), and OAT drug (methadone or buprenorphine).

RESULTS

A total of 10,251 people accessed OAT in Ireland in March 2019 (2 % buprenorphine, n = 178), increasing to 11,441 (4 % buprenorphine, n = 471) in March 2021. The study observed an immediate (β₂ = 504.3, p < 0.001) and continued (β₃ = 31.9, p < 0.001) increase of people accessing treatment following the introduction of the OAT contingency guidelines. In contrast, observed changes in level and slope were not significant for treatment initiation or dropout. The study did find, however, a modest reduction in dropout among those receiving buprenorphine (β₃ = -0.6, p = 0.036).

CONCLUSIONS

Changes introduced to the delivery of OAT, under the COVID-19 contingency guidelines, are associated with increased access to OAT in Ireland, with no evidence of increase in treatment dropout. Whether these effects will be maintained over time remains to be seen.

Consensus recommendations for opioid agonist treatment following the introduction of emergency clinical guidelines in Ireland during the COVID-19 pandemic: A national Delphi study

BACKGROUND

Emergency contingency guidelines for opioid agonist treatment (OAT) were introduced in Ireland in March 2020, to ensure rapid and uninterrupted access to treatment while mitigating COVID-19 risk. The contingency guidelines deviated, across multiple clinical domains, from pre-pandemic clinical guidelines published in 2016. The objectives of this study are to (1) identify changes introduced to OAT clinical guidelines in Ireland during the pandemic; and (2) develop consensus on whether the new recommendations should be retained beyond the pandemic, using a national Delphi consensus methodology.

METHODS

Clinical guidance recommendations ('statements') were generated by comparing the newly established contingency guidelines with the national 2016 Clinical Guidelines for OAT. Over two rounds of on-line Delphi testing, a panel of experts (people currently accessing OAT, psychiatrists, general practitioners, community pharmacists, a nurse, a psychologist and support/key workers) independently rated their agreement with each statement and provided comments. Statements with a median score of 4 or 5 and a lower quartile of ≥4 were classified as having reached consensus.

RESULTS

Forty-eight panel members were recruited, with a high participation level at Round 2 (90%, n=43). Consensus was achieved for 12 of the 19 statements at Round 1. The 7 remaining statements were revised, with 2 new statements, resulting in 9 statements at Round 2. Four statements reached consensus at Round 2. The final list includes 16 clinical guidance statements; 9 relating to assessment, 3 to OAT drug choice and dosing, 1 to take-away doses, 2 to overdose prevention and 1 to the continuation of e-prescriptions.

CONCLUSIONS

A wide range of stakeholders involved in the delivery and receipt of OAT agreed on 16 clinical guidance statements for inclusion in OAT clinical guidelines as we move beyond the pandemic, rather than reverting to pre-pandemic guidelines. The agreed statements relate to facilitating safe access to OAT with minimal waiting time, supporting patient-centred care to promote health and well-being, and preventing drug overdose. Notably, consensus was not achieved for OAT drug dosage and frequency of urine testing during the stabilisation and maintenance phase of care.

Comparing characteristics of suicide to non-suicide drug poisoning deaths, by sex, in Ireland

BACKGROUND

Suicide by drug poisoning is potentially preventable; however, evidence on associated risk factors by sex is limited.

AIM

To assist in understanding how individual and social contextual factors, and specific drugs, influence risk of suicide compared to non-suicide drug poisoning deaths, and how this differs by sex.

METHODS

Data were extracted from the National Drug-Related Deaths Index. Analysis included univariable and multivariable logistic regression to estimate unadjusted and adjusted odds ratios (OR) and 95% confidence intervals (CI) for factors associated with suicide drug poisoning deaths (SDPD) (primary outcome) compared with non-suicide drug poisoning deaths (NSDPD) and stratified by sex.

RESULTS

SDPD accounted for 240 (22%) of 1114 poisoning deaths, the majority among men (n = 147, 61%). Increasing age, mental ill health (AOR 7.85, 95% CI: 5.46-11.28), chronic pain (AOR 5.57, 95% CI: 3.28-9.46), and history of previous overdose (AOR 5.06, 95% CI: 3.39-7.56) were associated with increased odds of SDPD, with similar results for both sexes. The main drugs associated with SDPD were non-opioid analgesics (OR 4.06 [95% CI 2.66-6.18]), antipsychotics (OR 2.42 [95% CI 1.63-3.60]) and antidepressants (OR 2.18 [95% CI 1.59-2.97]). Pregabalin was associated with SDPD among women only.

LIMITATIONS

Secondary analysis of coronial data on drug poisoning deaths therefore findings may not be relevant to suicide deaths in general.

CONCLUSIONS

Ongoing monitoring for signs of suicidal intent in individuals with mental illness, chronic pain, overdose, and/or prescribed mental health medications may identify individuals in need of additional intervention.

Endogenous opiates and behavior: 2020

This paper is the forty-third consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2020 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

Trends in drug poisoning deaths, by sex, in Ireland: a repeated cross-sectional study from 2004 to 2017

OBJECTIVE

To examine sex differences in age-standardised rates (ASR) of overall and drug-specific drug poisoning deaths in Ireland between 2004 and 2017.

DESIGN

Repeated cross-sectional study.

SETTING

Drug poisoning deaths in Ireland.

PARTICIPANTS

National Drug-Related Deaths Index and pharmacy claims database (Primary Care Reimbursement Service-General Medical Services) data from 2004 to 2017.

OUTCOME MEASURES

The primary outcome was trends in drug poisoning death rates by sex. The secondary outcomes were trends in drug poisoning death rates involving (1) any CNS (Central Nervous System) depressants, (2) ≥2 CNS depressants and (3) specific drugs/drug classes (eg, prescription opioids, benzodiazepines, antidepressants, alcohol, cocaine and heroin) by sex. Joinpoint regression was used to examine trends, stratified by sex, in the ASR of drug poisoning deaths (2004-2017), change points over time and average annual percentage changes (AAPCs) with 95% CI.

RESULTS

Increased ASR for all drug poisoning deaths from 6.86 (95% CI 6.01 to 7.72) per 100 000 in 2004 to 8.08 (95% CI 7.25 to 8.91) per 100 000 in 2017 was mainly driven by increasing deaths among men (AAPC 2.6%, 95% CI 0.2 to 5.1), with no significant change observed among women. Deaths involving ≥2 CNS depressants increased for both men (AAPC 5.6%, 95% CI 2.4 to 8.8) and women (AAPC 4.0%, 95% CI 1.1 to 6.9). Drugs with the highest significant AAPC increases for men were cocaine (7.7%, 95% CI 2.2 to 13.6), benzodiazepines (7.2%, 95% CI 2.9 to 11.6), antidepressants (6.1%, 95% CI 2.4 to 10.0) and prescription opioids (3.5%, 95% CI 1.6 to 5.5). For women, the highest AAPC was for antidepressants (4.2%, 95% CI 0.2 to 8.3), benzodiazepines (3.3%, 95% CI 0.1 to 6.5) and prescription opioids (3.0%, 95% CI 0.7 to 5.3).

CONCLUSION

Drugs implicated in drug poisoning deaths vary by sex. Policy response should include prescription monitoring programmes and practical harm reduction information on polydrug use, especially CNS depressant drugs.

Impact of the COVID-19 pandemic on opioid agonist treatment in Ireland: Protocol for an interrupted time series analysis

While opioid agonist treatment (OAT) is the most effective treatment for opioid dependence, it is heavily dependent on regular face-to-face healthcare delivery placing both clients and treatment providers at risk of COVID-19. Following the emergence of COVID-19, policies were rapidly changed in Ireland, with the introduction of national contingency guidelines by the HSE National Social Inclusion Office, beginning in March 2020 to ensure rapid and uninterrupted access to OAT while balancing efforts to mitigate COVID-19 risk. This study aims to assess the impact of the national contingency guidelines, on the quality of OAT care delivered in Ireland. An interrupted time series analysis will be conducted using anonymised aggregated level data obtained from the Central Treatment List (CTL), the national register of people receiving OAT, administered by the National Drug Treatment Centre Board on behalf of the HSE. Separate segmented regressions will be conducted to estimate the impact of the national contingency guidelines on the following outcomes: (1) number of patients in treatment; (2) number of patients starting OAT; (3) average waiting time for treatment; (4) number of people on waiting list; (5) number of patients dropping out of treatment.  The study period will be divided into pre-(March 2019 to February 2020) and post- intervention (April 2020 to March 2021) segments. Immediate (change in level) and longer-term impacts (change in slope) of changes to provision of OAT in each of the outcomes will be investigated. Regression coefficients (β) and 95% confidence intervals (CIs) will be reported.

Development of quality indicators for the continued and safe delivery of Opioid Agonist Treatment (OAT), throughout and beyond COVID-19, using a Delphi Consensus technique

Opioid agonist treatment (OAT) is the most effective treatment for opioid dependence, although it relies heavily on regular face-to-face healthcare delivery. Following the emergence of COVID-19, policies were rapidly changed in Ireland to reduce the risk of contracting the virus for both clients and treatment providers. From March 2020, the Health Service Executive (HSE) National Social Inclusion Office introduced a series of national contingency guidelines, to ensure fast and uninterrupted access to OAT while balancing efforts to mitigate COVID-19 risks. The Programme for Government 2020 states they will retain many of the measures introduced during the COVID-19 pandemic to reduce waiting times in accessing treatment services and reduce overdose mortality. It is therefore essential to examine the impacts, benefits and unintended consequences of the special measures introduced during COVID-19 at a national level, thus informing which measures can and should be sustained throughout and beyond COVID-19 to support effective, safe and patient-centered care promoting the health and wellbeing of all people with opioid dependence. The aim of this project is to identify priorities for quality improvements which will inform clinical decision making throughout and beyond the pandemic. This will be achieved through a Delphi consensus study. Quality indicators will be identified by comparing the national contingency guidelines with the national 2016 Clinical Guidelines. The project steering group will review the proposed indicators, and the agreed quality indicators will be integrated into an on-line Delphi questionnaire. One hundred participants will be invited to form the Delphi consensus panel and will include a wide range of stakeholders, including people accessing OAT services, general practitioners, pharmacists and outreach workers. Evidence generated from this study will inform national policy decisions in relation to improving quality of care in OAT.

Response of tertiary addictions services to opioid dependence during the COVID-19 pandemic

The emergence of the COVID-19 pandemic has presented the addiction services with an unprecedented set of challenges. Opioid users are particularly vulnerable because of their high level of pre-existing health problems and lifestyle factors. In order to minimise their risks to self and to others in the current Covid-19 crisis, addiction services sought to urgently identify vulnerable individuals, and induct them into opioid substitution treatment (OST) promptly. Additionally, several guidelines were created and regularly updated by the health and safety executive (HSE) for any healthcare staff working with opioid users. These include guidance documents, to facilitate prompt induction of patients onto the OST programme, the prescribing of naloxone to all patients at risk of overdose, eConsultation, medication management for those in self-isolation, and the delivery of injecting equipment. The guidance documents and resources will provide a template for a new way of working for the sector during these challenging times and into the future.

Factors associated with early and later dropout from methadone maintenance treatment in specialist addiction clinics: a six-year cohort study using proportional hazards frailty models for recurrent treatment episodes

BACKGROUND

Retention in methadone maintenance treatment (MMT) is associated with reduced illicit drug use, criminal activity, and mortality; however, many clients move in and out of MMT. This study aims to identify determinants of time to dropout of MMT across multiple treatment episodes in specialist addiction services in Ireland.

METHODS

Cohort study of persons attending specialist addiction clinics between 2010 and 2015. MMT episodes were periods of continuous treatment if there were no interruptions to treatment lasting > 7days. Proportional hazards frailty models were used to assess factors associated with time to dropout from recurrent MMT episodes at 3 (90 days) and 12 months (91-365 days). MMT episodes were right- censored at time of death, transfer to prison or primary care, and study end.

RESULTS

A total of 2,035 individuals experienced 4,969 MMT episodes, with 2,724 dropout events during the six-year follow-up. Factors associated with dropout at 3 months included low dose methadone (<60 mg/day) (HR = 1.49, 95% CI 1.29-1.73) and previous dropout (HR = 1.65, 95% CI 1.41-1.92). Adherence was protective (HR = 0.91, 95% CI 0.90-0.92). Dropout at 12 months was associated with low dose methadone (HR = 1.44, 95% CI 1.23-1.68), previous dropout (HR = 1.37, 95% CI 1.16-1.61), males (HR 1.26, 95% CI 1.06-1.50), benzodiazepines (HR = 1.22, 95% CI 1.03-1.45) and number of comorbidities (HR = 1.12, 95% CI 1.05-1.20); adherence was protective (HR = 0.86, 95% CI 0.84-0.87).

CONCLUSIONS

Clients with a previous history of treatment dropout and those on low dose methadone should be identified as high risk for both early and later dropout. Inversely, adherence to treatment, not missing methadone doses, is protective.

Do interruptions to the continuity of methadone maintenance treatment in specialist addiction settings increase the risk of drug-related poisoning deaths? A retrospective cohort study

AIMS

To examine the risk of mortality associated with interruptions to the continuity of methadone maintenance treatment (MMT), including transfers between services, in opioid-dependent individuals attending specialist addiction services.

DESIGN

Retrospective cohort study using addiction services and primary care dispensing records, the National Methadone Register and National Drug-Related Death Index (NDRDI).

SETTING

Geographically defined population in Dublin, Ireland.

PARTICIPANTS

A total of 2899 people prescribed and dispensed methadone in specialist addiction services between January 2010 and December 2015. There were five exposure groups: weeks 1-4 following transfer between treatment providers; weeks 1-4 out of treatment; weeks 5-52 out of treatment; weeks 1-4 of treatment initiation; and weeks 5+ of continuous treatment (reference category).

MEASUREMENTS

Primary outcome: drug-related poisoning (DRP) deaths. Secondary outcome: all-cause mortality (ACM). Mortality rates calculated by dividing number of deaths (DRP; ACM) in exposure groups by person-years exposure. Unadjusted and adjusted Poisson regression (covariates age, sex, incarceration, methadone dose and comorbidities) estimated differences in mortality rates.

FINDINGS

There were 154 ACM deaths, 55 (35.7%) identified as DRP deaths. No deaths were observed in the first month following transfer between treatment providers. The risk of DRP mortality was highest in weeks 1-4 out of treatment [adjusted relative risk (aRR = 4.04, 95% confidence interval (CI) = 1.43-11.43, P = 0.009] and weeks 1-4 of treatment initiation (ARR = 3.4, 95% CI = 1.2-9.64, P = 0.02). Similarly, risk of ACM was highest in weeks 1-4 out of treatment (ARR = 11.78, 95% CI = 7.73-17.94, P < 0.001), weeks 1-4 of treatment initiation (aRR = 5.11, 95% CI = 2.95-8.83, P < 0.001) and weeks 5-52 off treatment (aRR = 2.04, 95% CI = 1.2-3.47, P = 0.009).

CONCLUSIONS

Interruptions to the continuity of methadone maintenance treatment by treatment provider do not appear to be periods of risk for drug-related poisoning or all-cause mortality deaths. Risk of drug related poisoning and all-cause mortality deaths appears to be greatest during the first 4 weeks of treatment initiation/re-initiation and after treatment cessation.