Chronic obstructive pulmonary disease in heroin users: An underappreciated issue with clinical ramifications

Abstract

Chronic Obstructive Pulmonary Disease (COPD) is prevalent amongst heroin users and is not restricted to smokers of the drug. This editorial discusses the extent of the problem, its implications for heroin overdose risk, and strategies to address this underappreciated issue. Chronic obstructive pulmonary disease (COPD) is common among heroin users, particularly smokers of heroin, occurring at rates well in excess of the general population [1-3]. There is evidence of both early onset and accelerated progression [4], with fatalities secondary to respiratory failure occurring before the age of 40 years reported [5]. Although often present from a younger age than is expected in smokers or the general population, COPD often goes underdiagnosed and undertreated in heroin users [1, 3], as do many health complications in this population. The health of heroin users is generally poor, the general presentation being one of accelerated aging. A great deal of attention given to the health of this population concerns blood borne viruses such as hepatitis C and chronic liver disease. Far less attention is given to COPD, a group of conditions characterized by persistent airflow limitations, which may have major implications for the risk of opioid overdose. Heroin users have several risk factors for COPD. First, although the prevalence of tobacco smoking has declined markedly in most Western countries, the prevalence of smoking among heroin users exceeds 90% [6, 7]. Second, the smoking of heroin has become a more common route of administration among heroin users, a practice that causes local airway irritation from heroin fumes [5]. The risk of a diagnosis of COPD is associated with more frequent and prolonged heroin smoking [8]. Finally, the injection of tablet preparations, which contain insoluble filler materials such as talc, or of heroin contaminated with such substances, may result in pulmonary foreign body granulomatosis that causes scar tissue formation [9]. Given these risk factors, how common is early onset COPD among heroin users? It is estimated that 40% of heroin users meet criteria for COPD [1]. Among smokers of heroin, the prevalence is as high as 50% [2, 4, 5, 8] and a fifth among injectors [1, 2, 10, 11]. In a recent case series of heroin overdose deaths, almost all of whom were injectors, a fifth was diagnosed with COPD at autopsy [12]. This is a probable underestimate as, unless in an advanced stage, emphysema can be difficult to diagnosis at routine post-mortem. As the cohort of heroin users age, it is likely that the prevalence of COPD among this population will increase [l]. Adverse outcomes related to these high rates are evidenced in the 10- to 15-fold risk of death due to respiratory disease among heroin users compared to the general population [13, 14]. There is evidence that COPD progresses at an accelerated rate among heroin users: Nightingale and colleagues [4] demonstrated a decline in forced expiratory volume in 1 second (FEV1) of 90 mL per year among heroin smokers diagnosed with COPD. This high level of decline in FEV1 exceeds the age-related decline observed in both tobacco smokers with COPD and healthy non-smokers. Heroin smokers also account for disproportionally high rates of hospitalizations for COPD exacerbations and they experience poorer outcomes following care, such as higher re-admission rates and greater need for use of non-invasive ventilation [15]. These high levels of COPD have implications for overdose risk and prevention among heroin users. The main risk that opioids pose for mortality, and ‘near misses’, is overdose. Opioids are central nervous system depressants, and the mechanism of overdose is respiratory depression, although cardiac arrest may occur secondary to myocardial oxygen deprivation [16]. Even among tolerant heroin users, respiration rates are suppressed and severe respiratory depression may persist long after the peak blood concentration has passed [17]. Opioids are also emetics and cough suppressants, and aspiration of vomitus and aspiration pneumonia is frequently seen in overdose [18]. Heroin is frequently used with other depressants, such as benzodiazepines and alcohol, further depressing respiration. The reduced respiratory reserve associated with COPD would be expected to increase the risk of death in the presence of respiratory depressants. Moreover, those with COPD would be at greater risk in the case of aspiration. The use of highly potent opioids with powerful respiratory depressant effects, such as fentanyl and fentanyl analogues, would be expected to increase further the risk of overdose among those with reduced respiratory reserve. The effects on lung function of smoking these drugs remain unknown. What are the clinical implications of such high rates of COPD? Given the stigma associated with heroin use, and the consequent barriers to treatment in the general medical settings, co-care in settings that provide services to heroin users, such as opioid substitution clinics, residential rehabilitation and needle and syringe programs, may provide venues for the diagnosis and treatment of COPD. Regular screening by spirometry would appear good clinical practice in such settings. Although this has been proposed for heroin smokers [7], the high rates among injectors indicate that a broader approach is needed [1]. Such screening is relevant to the quality of life of heroin users and to their risk of death from opioid-induced respiratory depression. Many such venues would not currently have access to high-quality spirometry, but investment in such technology may reduce the overall burden of disease among this population. In terms of the treatment of heroin dependence, buprenorphine maintenance has been shown to have reduced overdose mortality risk compared to methadone maintenance for older patients and those with physical comorbidities [19]. This, in all probability, is because of the mixed antagonist/agonists properties of buprenorphine and its lower level of respiratory depression compared to methadone (a pure agonist). For heroin users with COPD, buprenorphine would appear the prudent clinical choice of a maintenance drug. The provision of take-home naloxone is warranted for all heroin users, but is particularly salient for those with COPD. Finally, tobacco smoking cessation is a priority. Although this may seem a secondary issue in light of heroin dependence, it is clearly one that has implications for the morbidity and mortality of the heroin using population. COPD is prevalent among heroin users and not just among smokers of heroin. From the perspective of both global health and greater overdose risk, this is an issue that clinicians should be vigilant to. Shane Darke: Conceptualization (lead); writing—original draft (lead); writing—review and editing (lead). Michael Farrell: Conceptualization (supporting); writing—original draft (supporting); writing—review and editing (supporting). Johan Duflou: Conceptualization (supporting); writing—original draft (supporting); writing—review and editing (supporting). Julia Lappin: Conceptualization (supporting); writing—original draft (supporting); writing—review and editing (supporting). This work was funded by the National Drug and Alcohol Research Centre at the University of New South Wales. The National Drug and Alcohol Research Centre is supported by funding from the Australian Government. M.F. has received untied educational grants from Seqirus, Mundipharma and Indivior for postmarketing surveillance of pharmaceutical opioids. This organization had no role in this Editorial, and funding support was for work unrelated to this project. M.F. has received untied educational grants from Seqirus, Mundipharma and Indivior for post-marketing surveillance of pharmaceutical opioids. N/A.

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