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1 Introduction

In the United States , 100 million adults suffer from chronic pain [1] and approximately one third of primary care patients are diagnosed with chronic non-cancer pain [2]. In recent years, opioid therapy has been a common treatment modality for chronic pain [3] and the rates of opioid prescribing nearly doubled between 2000 and 2010 [4]. Yet overreliance on these medications may led to pharmacologic tolerance, opioid-induced hyperalgesia [5], and in some cases abuse of opioids [6]. Additionally, a significant proportion of people with opioid use disorder experience chronic pain. Within opioid substitution programs, as many as 60 % of patients are diagnosed with chronic pain [7]. Considering the potential iatrogenic consequences of long-term opioid regimens for chronic pain, opioid therapy may be inappropriate for many individuals with opioid use disorder, necessitating alternative analgesic pharmacotherapies and other non-pharmacologic pain treatment approaches.

2 Comorbid Chronic Pain and Opioid Use Disorders

Chronic pain is associated with psychological distress, decreased mobility, obesity, limited physical function, social isolation, financial strain, and chronic disability [8]. Many of the factors that exacerbate chronic pain are also related to increased vulnerability to abuse opioids [9]. This has been supported by studies suggesting that the majority of patients involved in opioid replacement therapy have also been diagnosed with chronic pain [7], and in some instances, patients first developed an opioid use disorder after being prescribed opioid medication for the treatment of pain [10]. Additionally, inadequately managed pain in patients with an opioid use disorder has been associated with increased risk for continued opioid misuse [11]. Tailored treatment plans for comorbid chronic pain and opioid use disorder may thus need to simultaneously address the entire sequelae of chronic pain and addiction.

3 Challenges to Managing Chronic Pain in Patients with Comorbid Opioid Use Disorders

Management of chronic pain often includes the use of opioid medication. Precautions for the use of chronic opioid therapy should be employed with any patient with a history of an opioid use disorder due to the heightened risk for abuse. Patients who meet criteria for an opioid use disorder are at heightened risk for chronic pain relative to patients without a history of opioid use disorder (e.g. [7]). Among individuals receiving methadone maintenance treatment, up to 60 % are diagnosed with a chronic pain condition (e.g. [12,13]) and those who report abuse of prescription opioids in the past month are more likely to endorse chronic pain [14]. Unfortunately, few patients receiving opioid substitution therapy receive concurrent non-opioid pain management interventions [15]. Thus, some patients who over-medicate with opioids to manage pain may not be addressing a root cause of their opioid addiction. These patients may also be poor responders to singular pain treatment approaches. Studies indicate that individuals with concurrent chronic pain and opioid use disorders are at a heightened risk for poor pain treatment response, including continued functional impairment, maintenance of illicit substance use, and fatality (e.g. [12,16–18]).

The poor outcomes for this population may be due to the unique challenge of simultaneously treating two potentially debilitating disorders. This challenge is further complicated by the seemingly discrepant treatment objectives for each disorder. Historically, treatment for opioid use disorder intends to restore functioning by reducing drug use, while pain management attempts to restore functioning through analgesia [19]. When multiple providers, without an agreed upon treatment plan and objectives, treat the same patient for comorbid opioid use disorder and chronic pain, tension might arise due to the differing treatment approaches for each condition. Similarly, evidence suggests that if the burden of pain treatment falls upon a single provider, concern regarding the potential abuse of prescribed opioids and the lack of definitive clinical guidelines may lead to the under-treatment of pain in this population [20]. Although hesitation by providers to employ pain management interventions with this population has been documented, evidence suggests that patients with opioid use disorders who receive pain treatment endorse significant pain-related improvements [15].

4 Clinical Guidelines for the Management of Chronic Pain in Patients with Co-occurring Opioid Use Disorder

The American Pain Society and the American Academy of Pain Medicine developed a Pain Medicine Opioids Guidelines Panel to formulate recommendations regarding the long-term use of opioids to manage chronic pain. Due to the risk of aberrant drug-related behaviors , they propose intense monitoring be conducted for patients with a comorbid substance use disorder, in conjunction with behavioral therapies, and that chronic opioid therapy be discontinued if there is evidence of diversion or medication noncompliance [21]. The guidelines specify that although opioid medication may be risky for some patients with a history of substance abuse, it is not presumed that opioid medication is inappropriate treatment for all patients with a past history of a substance use disorder. Specific recommendations include frequent and intense pain reassessment to further improve pain-related outcomes, regular monitoring, including urine drug screens, limited prescription quantities, consultation or co-management with a mental health or substance use disorder provider, and use of prescription monitoring programs, if available, to identify when an individual is acquiring opioid medication from multiple providers (e.g. [22,23]). In addition, motivational counseling may be indicated to regularly reinforce a patient’s motivation to adhere to the prescribed treatment plan, despite ongoing triggers to misuse or abuse substances [24]. These guidelines highlight the importance of a multidisciplinary approach to pain management in patients with opioid and other substance use disorders, as it may be unmanageable for a single provider or discipline to adequately address all aspects of chronic pain in patients with comorbid opioid use disorder.

5 Models of Pain Treatment

The growing demand for pain management has resulted in greater awareness to treating chronic pain and a variety of treatment models. Pain treatment approaches fall along a continuum from least to most comprehensive. Typically, a patient is initially prescribed analgesic pharmacotherapy through primary care, and if unresponsive to this treatment, is referred to one or more specialty services. The most basic treatment model is that of a single service clinic or modality-oriented clinic. This type of outpatient clinic provides a single treatment for pain, but often lacks the personnel and clinical expertise to provide a comprehensive pain assessment or pain treatment plan. Services within these clinics vary greatly, but examples include an acupuncture, biofeedback, physical therapy, or occupational therapy clinic. A single service clinic may be appropriate and most valuable for individuals living with mild forms of chronic pain, who have yet to develop significant pain-related disability. For patients whose pain is not adequately managed through a single treatment modality, more comprehensive pain treatment approaches may be required.

A more complex model of care is that of a pain clinic, which provides pain interventions that often target one pain condition, such as headache or back pain. Pain clinics may employ individuals from more than one discipline and can provide more comprehensive assessment and management of chronic pain than what is available in single service clinics. Nevertheless, pain clinics are often limited in the variety of services provided. Pain clinics commonly refer patients to outside providers for services that are not available within the clinic. This can result in fragmented patient care due to inconsistent communication and conflicting treatment orientations between providers in different clinics or healthcare systems. Patients also face the burden of keeping appointments across multiple clinics that can sometimes be geographically distant.

Multidisciplinary Pain Clinics (MPCs) are comprehensive, specialized inpatient or outpatient clinics composed of multiple pain-related disciplines. Clinical services often include physical therapy, occupational therapy, physical medicine and rehabilitation, pain education, and psychological/behavioral pain interventions. By providing global and intensive assessment and treatment interventions, MPCs are equipped to treat moderate-to-severe chronic pain that has resulted in diminished psychosocial functioning. The Commission on Accreditation of Rehabilitation Facilities (CARF) is the international accrediting body for MPCs. At the time of this writing, according to the CARF website (http://www.carf.org/home/), there are currently 69 accredited MPCs in the United States [25]. MPCs strive to improve psychosocial functioning and global life satisfaction by targeting the various factors that are maintaining or exacerbating the impairments one experiences as a result of chronic pain.

6 Disciplines Represented Within Multidisciplinary Pain Clinics

Significant variability exists across MPCs in the combination of pain treatments used for individual patients. This may partly be due to the notion that MPCs do not follow a single protocol to be used for all patients. Rather providers from various disciplines collaborate to identify what interventions may be most effective in addressing the unique impairments for each patient [26]. MPC staff typically comprise Physical Medicine and Rehabilitation Physicians, Nurses, Psychologists, Physical and Recreational Therapists, Social Workers, and Pharmacists. Some MPCs also include a Neurosurgeon, Orthospine Surgeon, Interventional Pain Specialist, and a Patient Advocate [27].

7 Advantages of Multidisciplinary Pain Clinics

The diversity of staff within an MPC naturally lends itself to a biopsychosocial conceptualization, assessment, and treatment of chronic pain. A biopsychosocial model of care assumes that a disorder is impacted by dynamic physiological, psychological, and social factors that interact to perpetuate, or worsen, symptoms [28]. This approach has widely replaced that of the dated biomedical model for chronic pain [29], which conceptualizes pain as solely affected by physical processes and does not consider the impact of social or psychological factors on the pain experience.

Potential contributions to a patient’s pain that should be assessed include pain and general medical history, functional impairments, current and prior medications, past treatment compliance, previously tried procedures and interventions, legal history, social development, psychiatric history, and substance use history [30]. Due to the complexity of forming such a holistic conceptualization, the use of a multidisciplinary team is paramount. Involving experts from various disciplines in the assessment process helps to ensure that all relevant information is obtained. An MPC also ameliorates the burden of a single provider conducting the complete evaluation and ensures that clinicians only assess areas in which they have expertise.

Treatment within MPCs also applies a biopsychosocial approach. The application of multimodal evidence-based interventions to simultaneously target pain reduction and functional restoration aids in addressing the multiple contributors to a patient’s pain. Effective interventions for comorbid opioid use disorder and chronic pain may include medication, substance use treatment, behavioral interventions, psychotherapy, weight loss, physical mobility, and conditioning [31]. Bearing in mind the assorted interventions necessary to improve functioning, it is vital that the various providers regularly collaborate to determine when modifications to the treatment plan should be implemented. Additionally, MPCs facilitate careful monitoring of the treatment regimen. This allows for input to be received from all disciplines, and modifications to be coordinated, before changes to the treatment plan are made.

8 Treatment Efficacy and Cost-Effectiveness

Considering the large number of patients who seek pain management and the rates of comorbidity between chronic pain and opioid use disorder, efficient and economical pain rehabilitation is needed. Unfortunately, conventional single service medical treatments have not demonstrated consistent efficacy or cost-effectiveness [32]. MPCs, on the other hand, have demonstrated superior outcomes across a number of studies and may produce long-term systemic cost benefits by reducing disability, lost work productivity, and the frequency with which high-cost services (e.g., emergency department visits and inpatient hospitalizations) are utilized by patients [32]. A review of evidence-based treatments for chronic pain demonstrated the efficacy of MPCs and identified that annual medical costs following treatment by an MPC were reduced by over 68 % [32]. Further, the review found that more than two thirds of individuals treated by an MPC returned to work, compared to a little over one quarter of patients treated by single service models. These findings suggest that MPCs have a smaller economical cost in regard to lifetime disability and healthcare utilization, despite the increased cost at the onset of treatment.

9 Challenges/Considerations of Multidisciplinary Pain Clinics

Despite research to suggest the superiority and long-term cost-effectiveness of MPCs, there are unique challenges facing patients and providers who wish to utilize a multidisciplinary team. There are multiple stakeholders who impact healthcare access and barriers. For chronic pain, these stakeholders include, but are not limited to, the patient who is most likely interested in symptom management, third-party payers who may be interested in reducing future treatment utilization, and employers and worker compensation boards that are interested in closing claims by returning workers back to meaningful employment. The diverse players impacting the assessment and treatment of chronic pain can create a complex and politicized dimension to treatment.

Unfortunately, due to common cost-containment policies of third-party payers [32], many patients are unable to initiate treatment with an MPC. Moreover, the number of MPCs appears to be decreasing. The number of CARF-accredited MPCs in the United States is steadily decreasing from 210 in 1998, 84 in 2005 [33], to currently 69. The conflict between what has been found to be most effective for treating pain, the constraints of third-party payers, and the limitations of individual providers may prevent many patients from receiving the gold standard of evidence-based pain treatment and patients may, as a result, experience suffering from either untreated or undertreated pain. This in turn may lead to or perpetuate existing patterns of opioid misuse or abuse.

10 Conclusion

There is growing concern regarding the treatment of chronic pain and the associated risks of long-term opioid therapy, due to the threat of opioid misuse and abuse. The risk of iatrogenic effects of opioid therapy is greater for patients with a comorbid substance use disorder. Various treatment modalities exist for managing chronic pain, but considering the complex presentation of patients with comorbid chronic pain and opioid use disorder, MPCs may be the most appropriate pain treatment modality to address the complex and multifaceted needs of this patient population. Advantages of utilizing an MPC for this population include a comprehensive conceptualization of the biopsychosocial factors that influence pain and illicit opioid use behaviors, as well as coordinating various interventions to simultaneously target those factors. However, given the initial upfront cost associated with MPC treatment and reimbursement challenges in a third-party payer healthcare system, MPCs may not be available to many patients who could benefit from these services.