Chronic pain and hepatitis C virus infection in opioid dependent injection drug users

Pain in people seeking and receiving opioid agonist treatment: A systematic review and meta-analysis of prevalence and correlates

BACKGROUND AND AIMS

People with opioid use disorder (OUD) commonly experience pain including chronic pain. Despite the high prevalence, few studies have systematically examined the prevalence and correlates of pain among people seeking or receiving opioid agonist treatment (OAT) for OUD. This review aimed to determine the prevalence of pain in this population globally, and estimate the association between chronic pain and other demographic and clinical characteristics.

METHODS

Electronic searches were conducted in three databases (Medline, Embase and PsycINFO) from the inception until October 2022. Eligible studies reported prevalence rates of current and/or chronic pain. Meta-analyses examining the main prevalence estimates were conducted by Stata SE 18.0, and comorbid clinical conditions were analysed by Review Manager 5.4.

RESULTS

Fifty-six studies (n participants = 35 267) from sixty-seven publications were included. Prevalence estimates of current and chronic pain were reported in 27 (48.2%) and 40 studies (71.4%), respectively. Most studies were conducted in North America (71.4%, n = 40) and used cross-sectional designs (64.3%, n = 36). Meta-analyses revealed a pooled prevalence of 60.0% (95% confidence interval [CI]: 52.0-68.0) for current pain and 44.0% [95% CI: 40.0-49.0] for chronic pain. Chronic pain was positively associated with older age (mean deviation of mean age: 2.39 years, 95% CI: 1.40-3.37; I2 = 43%), unemployment (odds ratio [OR] = 0.57, 95% CI: 0.42-0.76; I2 = 78%), more severe mental health symptoms (e.g. more severe depression (standardised mean difference [SMD] of mean scores: 0.45, 95% CI: 0.20-0.70; I2 = 48%) and anxiety symptoms (SMD: 0.52, 95% CI: 0.17-0.88; I2 = 67%), and hepatitis C (OR = 1.41, 95% CI: 1.03-1.94; I2 = 0%). No association was observed between chronic pain and the onset and type of OAT, geographic location, study design, survey year, participant age or use of specific pain assessment tools.

CONCLUSIONS

There appears to be a high prevalence of pain among people seeking or receiving opioid agonist treatment for opioid use disorder compared with the general population, with positive associations for older age, unemployment, hepatitis C and the severity of some mental health symptoms.

Chronic pain and infection: mechanisms, causes, conditions, treatments, and controversies

Throughout human history, infection has been the leading cause of morbidity and mortality, with pain being one of the cardinal warning signs. However, in a substantial percentage of cases, pain can persist after resolution of acute illness, manifesting as neuropathic, nociplastic (eg, fibromyalgia, irritable bowel syndrome), or nociceptive pain. Mechanisms by which acute infectious pain becomes chronic are variable and can include immunological phenomena (eg, bystander activation, molecular mimicry), direct microbe invasion, central sensitization from physical or psychological triggers, and complications from treatment. Microbes resulting in a high incidence of chronic pain include bacteria such as the Borrelia species and Mycobacterium leprae, as well as viruses such as HIV, SARS-CoV-2 and herpeses. Emerging evidence also supports an infectious cause in a subset of patients with discogenic low back pain and inflammatory bowel disease. Although antimicrobial treatment might have a role in treating chronic pain states that involve active infectious inflammatory processes, their use in chronic pain conditions resulting from autoimmune mechanisms, central sensitization and irrevocable tissue (eg, arthropathy, vasculitis) or nerve injury, are likely to cause more harm than benefit. This review focuses on the relation between infection and chronic pain, with an emphasis on common viral and bacterial causes.

Prevalence and Medication Treatment of Opioid Use Disorder Among Primary Care Patients with Hepatitis C and HIV

BACKGROUND

Hepatitis C and HIV are associated with opioid use disorders (OUD) and injection drug use. Medications for OUD can prevent the spread of HCV and HIV.

OBJECTIVE

To describe the prevalence of documented OUD, as well as receipt of office-based medication treatment, among primary care patients with HCV or HIV.

DESIGN

Retrospective observational cohort study using electronic health record and insurance data.

PARTICIPANTS

Adults ≥ 18 years with ≥ 2 visits to primary care during the study (2014-2016) at 6 healthcare systems across five states (CO, CA, OR, WA, and MN).

MAIN MEASURES

The primary outcome was the diagnosis of OUD; the secondary outcome was OUD treatment with buprenorphine or oral/injectable naltrexone. Prevalence of OUD and OUD treatment was calculated across four groups: HCV only; HIV only; HCV and HIV; and neither HCV nor HIV. In addition, adjusted odds ratios (AOR) of OUD treatment associated with HCV and HIV (separately) were estimated, adjusting for age, gender, race/ethnicity, and site.

KEY RESULTS

The sample included 1,368,604 persons, of whom 10,042 had HCV, 5821 HIV, and 422 both. The prevalence of diagnosed OUD varied across groups: 11.9% (95% CI: 11.3%, 12.5%) for those with HCV; 1.6% (1.3%, 2.0%) for those with HIV; 8.8% (6.2%, 11.9%) for those with both; and 0.92% (0.91%, 0.94%) among those with neither. Among those with diagnosed OUD, the prevalence of OUD medication treatment was 20.9%, 16.0%, 10.8%, and 22.3%, for those with HCV, HIV, both, and neither, respectively. HCV was not associated with OUD treatment (AOR = 1.03; 0.88, 1.21), whereas patients with HIV had a lower probability of OUD treatment (AOR = 0.43; 0.26, 0.72).

CONCLUSIONS

Among patients receiving primary care, those diagnosed with HCV and HIV were more likely to have documented OUD than those without. Patients with HIV were less likely to have documented medication treatment for OUD.

Smokers with opioid use disorder may have worse drug use outcomes after varenicline than nicotine replacement

INTRODUCTION

Smokers with opioid use disorder (OUD) have little success with smoking cessation, possibly due to interactions between nicotine and opioid receptor systems. Smokers with OUD versus non-opioid substance use disorders (NOUD) have not been compared for response to smoking treatment. Data to make this comparison came from our previous study of 12 weeks (plus dose run-up) of varenicline (VAR) versus 12 weeks of nicotine patch (NRT), in a double-placebo design.

METHODS

The current study reports secondary analyses comparing smokers with OUD (n = 47) and NOUD (n = 90) on pretreatment smoking, alcohol and drug use, intolerance of physical discomfort, smoking medication adherence, and 3- and 6-month smoking and substance use outcomes (by VAR versus NRT).

RESULTS

Smokers with OUD did not differ on pretreatment alcohol or smoking measures while reporting significantly more drug use days. Smokers with OUD versus NOUD had significantly fewer days adherent to VAR or placebo capsules but not to patches, and were more tolerant of physical discomfort. While smoking and heavy drinking days at follow-ups did not differ by diagnosis, smokers with OUD had significantly more drug use days in months 4-6 when assigned to VAR (16.4 days) than to NRT (8.1 days).

CONCLUSIONS

NRT might be a better choice than VAR for smokers with OUD due to lower adherence and more drug use days with VAR. However, this novel comparison of smoking pharmacotherapy response in smokers with OUD versus NOUD needs to be confirmed with larger numbers of participants.

Characterising the association between positive hepatitis C virus antibody and pain among people who inject drugs

INTRODUCTION AND AIMS

People who inject drugs (PWID) are a key group within the hepatitis C virus (HCV) pandemic. Chronic pain is a common condition among PWID as these individuals are often exposed to soft tissue infections due to injections and violence. This study aims to characterise the relationship between HCV exposure and pain among PWID.

DESIGN AND METHODS

Data were derived from three prospective cohorts of PWID in Vancouver, Canada, between December 2011 and November 2016. The primary outcome was pain severity, which was defined based on the Euroqol EQ-5D-3L pain subscale. A bivariable and multivariable ordinal generalised estimating equations model was used to quantify the association between HCV exposure and pain among participants.

RESULTS

One thousand and twelve of 2038 participants (50%) reported moderate/extreme pain at baseline. In total, 1473 (72%) participants were HCV-antibody positive. In unadjusted analyses, HCV exposure was positively associated with increased pain [odds ratio (OR) = 1.47; 95% confidence interval (CI): 1.20-1.81]. However, once adjusted for known confounders in multivariable analyses, HCV exposure did not remain significantly associated with increased pain (adjusted OR = 1.00; 95%CI: 0.78-1.28).

DISCUSSION AND CONCLUSIONS

In this sample of PWID, HCV exposure was not significantly associated with pain once other factors were considered. These various factors may explain the elevated risk of pain among PWID and should be addressed in future initiatives when managing pain among PWID with HCV exposure. Future studies should also examine whether pain changes with changes in HCV status (i.e. active vs. cleared infection).

Discomfort Intolerance in Relation to Asthma Outcomes

Anxiety symptoms and disorders are common among those with asthma and contribute to poorer health outcomes. Building on work examining anxiety-related cognitive-affective risk factors in asthma, the current study sought to explore associations between discomfort intolerance (i.e., the inability to withstand or tolerate unpleasant bodily sensations) in relation to lung function, asthma control, and quality of life. Participants were 61 adults with asthma (61.9% female; 54.8% African American; M age = 34.72, SD = 13.58) who were administered a self-report assessment battery and a lung function assessment. We found that, above and beyond the effects of anxiety sensitivity-physical concerns, greater discomfort intolerance was significantly associated with poorer lung function (9.5% variance), asthma control (9.9% variance), and overall asthma-related quality of life (11.7% variance) as well as the specific quality of life domains of activity limitations (12.6% variance) and asthma symptoms (6.8% variance). Thus, individuals with asthma who are unable to tolerate physical discomfort may be at risk for poor asthma outcomes and interventions to reduce discomfort intolerance could potentially be useful in this population.

Chronic Pain Opioid-Maintained Patients Receive Less Analgesic Opioid Prescriptions

Treating pain and opioid use disorder represents a clinical challenge. While most studies that have assessed opioid analgesic use in opioid substitution treatment (OST) patients primarily address opioid analgesic misuse (1, 2), only few studies focused on OST patients assessed the prescription of analgesic opioids for chronic pain. We sought to compare the prevalence of analgesic opioid prescription (AOP) in two groups of chronic non-cancer pain (CNCP) patients: OST patients vs. the general population. This was a population-based cross-sectional study based on the French national healthcare claims database SNIIRAM (Système National d'Informations Inter-Régimes de l'Assurance Maladie) covering over 66 million people (98.8% of the French population). Overall, 67,173 participants ≥15 years old undergoing continuous OST in 2015 ("OST patients" group) were included and age- and gender-matched by means of a 1:1 ratio with 67,173 patients without OST ("control" group). In each group, patients with cancer conditions were excluded and those having received opioid and non-opioid analgesics for at least 3 months were identified (CNCP patients). Compared to control patients, CNCP OST patients received less AOP (47.8 vs. 68.0%, p < 0.0001) and more often non-opioid prescription (52.2 vs. 32.0%, p < 0.0001). In multivariate analysis, CNCP OST patients were 2.7 times less likely to be prescribed analgesic opioids (adjusted odds ratio [OR] = 2.7 [2.42-3.01], p < 0.0001) than control patients. AOP correlated in CNCP OST patients with: age ≤ 40 years old, female gender, low-income status, methadone-maintained treatment, mental health disorder, hepatitis C virus (HCV) infection, and alcohol abuse disorder. Opioid analgesics were less often prescribed in CNCP OST patients. AOP prevalence was 2.7-fold lower than in the general population. Chronic pain management in OST patients needs to be reinforced through additional physician training and a multidisciplinary approach.

Physical pain is common and associated with nonmedical prescription opioid use among people who inject drugs

Background

People who inject drugs (PWID) often have poor health and lack access to health care. The aim of this study was to examine whether PWID engage in self-treatment through nonmedical prescription opioid use (NMPOU). We describe the prevalence and features of self-reported physical pain and its association with NMPOU.

Methods

PWID (N = 702) in San Francisco, California (age 18+) were recruited to complete interviewer administered surveys between 2011 and 2013. Multivariate logistic regression analysis was conducted to examine the associations among self-reported pain dimensions (past 24-h average pain, pain interference with functional domains) and NMPOU, controlling for age, sex, psychiatric illness, opioid substitution treatment, homelessness, street heroin use and unmet healthcare needs.

Results

Almost half of the sample reported pain, based on self-reported measures in the 24 h before their interview. The most common pain locations were to their back and lower extremities. Past 24-h NMPOU was common (14.7%) and associated with past 24 h average pain intensity on a 10 point self-rating scale (adjusted odds ratio [AOR] = 2.15, 95% confidence interval [CI] 1.21–3.80), and past 24 h pain interference with general activity (AOR 1.82 [95% CI 1.04–3.21]), walking ability (AOR 2.52 [95% CI 1.37–4.63]), physical ability (AOR 2.01 [95% CI 1.16–3.45]), sleep (AOR 1.98 [95% CI 1.13–3.48]) and enjoyment of life (AOR 1.79 [95% CI 1.02–3.15]).

Conclusion

Both pain and NMPOU are common among PWID, and highly correlated in this study. These findings suggest that greater efforts are needed to direct preventive health and services toward this population.

Pain Symptoms Associated with Opioid Use among Vulnerable Persons with HIV: An exploratory study with implications for palliative care and opioid abuse prevention

Current or former injection drug users with human immunodeficiency virus (HIV) are at high risk for pain, which adversely affects their quality of life and may increase their risk for illicit drug use or relapse. We explored associations between pain symptoms and substance use among injection-drug-using study participants with HIV who had histories of heroin use. Using generalized estimating equations and controlling for prior substance use, we found that pain in each six-month period was associated with the use of heroin and prescription opioids, but not the use of nonopioid drugs or alcohol. Routine clinical assessment and improved management of pain symptoms may be needed for persons with HIV and a history of injection drug use, particularly those with chronic pain, for whom there is increased risk for heroin use.

Clinical Comorbidities among Cocaine Users Screened in the Community through HealthStreet

OBJECTIVES

We investigated the differences in clinical characteristics and musculoskeletal (MSK) conditions by cocaine use.

METHODS

HealthStreet, a community engagement program assessed 7936 adults for medical conditions.

RESULTS

Among 6145 African Americans (77%) and 1791 (23%) Caucasians, 15.5 % and 25% reported cocaine use, respectively. African-American cocaine users were older (p < .001) and more likely to report hypertension (p < .001) and HIV (p <.001) than Caucasian users. Compared to non-users, back pain was reported by 42% of African Americans (p < .001) and 48% of Caucasian cocaine users (p < .003). African-American cocaine users had significantly higher odds of back pain, 1.60 (95% CI 1.27, 2.04) and arthritis, 1.40 (95% CI 1.19, 1.64) than Caucasians.

CONCLUSIONS

Cocaine users are more likely to endorse MSK conditions than non-users. Racial disparities among users existed; however, how race affects health among users requires further research.

Hepatitis C virus infection and pain sensitivity in patients on methadone or buprenorphine maintenance therapy for opioid use disorders

BACKGROUND

Patients with opioid use disorders on opioid agonist therapy (OAT) have lower pain tolerance compared to controls. While chronic viral infections such as HCV and HIV have been associated with chronic pain in this population, no studies have examined their impact on pain sensitivity.

METHODS

We recruited 106 adults (41 uninfected controls; 40 HCV mono-infected; and 25 HCV/HIV co-infected) on buprenorphine or methadone to assess whether HCV infection (with or without HIV) was associated with increased experimental pain sensitivity and self-reported pain. The primary outcome was cold pain tolerance assessed by cold-pressor test. Secondary outcomes were cold pain thresholds, wind-up ratios to repetitive mechanical stimulation (i.e., temporal summation) and acute and chronic pain. Multivariable regression models evaluated associations between viral infection status and outcomes, adjusting for other factors.

RESULTS

No significant differences were detected across groups for primary or secondary outcomes. Adjusted mean cold pain tolerance was 25.7 (uninfected controls) vs. 26.8 (HCV mono-infection) vs. 25.3 (HCV/HIV co-infection) seconds (global p-value=0.93). Current pain appeared more prevalent among HCV mono-infected (93%) compared to HCV/HIV co-infected participants (76%) and uninfected controls (80%), as did chronic pain (77% vs. 64% vs. 61%, respectively). However, differences were not statistically significant in multivariable models.

CONCLUSION

This study did not detect an association between HCV infection and increased sensitivity to pain among adults with and without HIV who were treated with buprenorphine or methadone for opioid use disorders. Results reinforce that pain and hyperalgesia are common problems in this population.

Patterns of, and Factors Associated With, Illicit Pharmaceutical Opioid Analgesic Use in a Prospective Cohort of People Who Inject Drugs in Melbourne, Australia

BACKGROUND

People who inject drugs (PWID) are a key population engaging in pharmaceutical opioid analgesic (PO) use, yet little is known about patterns of illicit PO use among this group.

OBJECTIVES

The aims of this research were to measure the prevalence and frequency of lifetime and past-month illicit PO use and injection in a sample of regular PWID, to examine patterns of past-month illicit PO use within individuals over time, and to identify factors independently associated with past-month illicit PO use.

METHODS

Data were drawn from a prospective cohort study of regular PWID (N = 666) in Melbourne, Australia. Data from five waves of annual data collection (including baseline) were analyzed descriptively and using generalized estimating equations (GEE).

RESULTS

At baseline, 59% of participants reported lifetime illicit PO use and 20% reported past-month use, predominantly through injecting. Most illicit PO users at baseline transitioned to nonuse of illicit POs across the study period. In multivariable GEE analysis, factors associated with past-month illicit PO use included past-year arrest [adjusted odds ratio (AOR): 1.39], opioids other than heroin as drug of choice (AOR: 5.14), experiencing poorer physical health (AOR: 0.98) and a range of other drug use variables.

CONCLUSIONS

We found little evidence of ongoing illicit PO use among those followed up, with illicit PO use linked to polydrug use more broadly. Nonetheless, trends in illicit PO use among PWID should continue to be monitored and harm reduction interventions implemented to reduce the associated public health risks.

Distress tolerance and use of antiretroviral therapy among HIV-infected individuals in substance abuse treatment

Despite recent clinical guidelines recommending early initiation and widespread use of antiretroviral therapy (ART), many HIV-infected individuals are not receiving ART-in particular low-income, minority substance users. Few studies have examined psychological, as opposed to structural, factors related to not receiving ART in this population. Perceived capacity to tolerate physical and psychological distress, known as distress tolerance (DT), may be a particularly relevant yet understudied factor. The current study tested the relationship between self-reported physical and psychological DT and ART receipt among predominantly low-income, minority HIV-infected substance users (n=77). Psychiatric disorders, biological indicators of health status, ART use, structural barriers to health care, and self-reported physical and psychological DT were assessed. 61% of participants were receiving ART. The only factors that distinguished individuals not on ART were greater avoidance of physical discomfort, higher psychological DT, and higher CD4 count. Both DT measures remained associated with ART use after controlling for CD4 count and were associated with almost a two-fold decrease in likelihood of ART receipt. Current findings suggest higher perceived capacity to tolerate psychological distress and greater avoidance of physical discomfort are important factors associated with lower ART use among substance users and may be important intervention targets.

Epidemiology of pain among outpatients in methadone maintenance treatment programs

BACKGROUND

This analysis explored the prevalence and correlates of pain in patients enrolled in methadone maintenance treatment (MMT).

METHODS

Patients in two MMT programs starting a hepatitis care coordination randomized controlled trial completed the Brief Pain Inventory Short-Form and other questionnaires. Associations between clinically significant pain (average daily pain≥5 or mean pain interference≥5 during the past week) and sociodemographic data, medical status, depressive symptoms, and health-related quality of life, and current substance use were evaluated in multivariate analyses.

RESULTS

The 489 patients included 31.8% women; 30.3% Hispanics, 29.4% non-Hispanic Blacks, and 36.0% non-Hispanic Whites; 60.1% had hepatitis C, 10.6% had HIV, and 46.8% had moderate or severe depressive symptomatology. Mean methadone dose was 95.7mg (SD 48.9) and urine drug screening (UDS) was positive for opiates, cocaine, and amphetamines in 32.9%, 40.1%, and 2.9%, respectively. Overall, 237 (48.5%) reported clinically significant pain. Pain treatments included prescribed opioids (38.8%) and non-opioids (48.9%), and self-management approaches (60.8%), including prayer (33.8%), vitamins (29.5%), and distraction (12.7%). Pain was associated with higher methadone dose, more medical comorbidities, prescribed opioid therapy, and more severe depressive symptomatology; it was not associated with UDS or self-reported substance use.

CONCLUSIONS

Clinically significant pain was reported by almost half of the patients in MMT programs and was associated with medical and psychological comorbidity. Pain was often treated with opioids and was not associated with measures of drug use. Studies are needed to further clarify these associations and determine their importance for pain treatment strategies.