Chronic pain and psychiatric illness: Managing comorbid conditions

Neuropathic pain can be addressed with certain antidepressants¹³—specifically, those that increase serotonin and norepinephrine (eg, tricyclic antidepressants [TCAs] and serotonin-norepinephrine reuptake inhibitors [SNRIs]), or medications that block ion channels (eg, anticonvulsants). TCAs (eg, desipramine, nortriptyline, amitriptyline) are among the best studied and most cost effective medications for treating neuropathic pain,^14,15 but they can have sedating and anticholinergic effects, as well as cardiac adverse effects (ie, prolongation of the QTc interval). SNRIs (eg, venlafaxine, desvenlafaxine, duloxetine, and milnacipran) can be effective and often are better tolerated than TCAs.¹⁴

Some newer anticonvulsants (eg, gabapentin and pregabalin) have been found to be more effective than placebo for a variety of neuropathic pain conditions.^16,17 Although they have few drug-drug interactions, anticonvulsants can cause dizziness, forgetfulness, and sedation. These adverse effects can be minimized by starting at a low dosage and titrating carefully. Because hepatic or renal impairment can affect metabolism or excretion of these drugs, review the prescribing information to determine safe dosing.

Targeted injection of medications to major pain generators (eg, an epidural steroid for radicular neck and back pain; facet injections for facet-related neck and back pain; trigger point injections for myofascial pain; occipital nerve blocks for occipital neuralgia; and botulinum toxin A injections for chronic migraine headache) can be effective in reducing discomfort and increasing function in patients with chronic pain. A detailed discussion of such therapies is beyond the scope of this article, but have been reviewed extensively elsewhere.^18,19

Opioids. Although there is little evidence of long-term efficacy with chronic opioid therapy for most patients, a trial of opioids might be warranted for select patients who do not respond to other medications. Because the risk–benefit ratio for chronic opioid therapy is high,^20-22 a decision to initiate a trial of a low-dosage opioid should be made only after careful consideration of those risks. It is generally agreed that treatment of chronic pain with low-dosage opioid therapy is more likely to be successful when it is used as an adjuvant to non-opioid modalities (eg, physical reconditioning, injection therapies, spinal cord stimulation, neurobehavioral interventions, non-opioid medications).

The Federation of State Medical Boards has stated that excessive reliance on opioid medications for treating chronic pain is a deviation from best practices.²³ To maximize benefit and minimize risk, clinicians should carefully select appropriate patients, establish functional goals, and regularly monitor for efficacy and compliance. Thoroughly document these steps in the patient’s record for later reference.²³

After establishing a clinical diagnosis for the cause of the pain, you should determine the risk of opioid abuse or misuse by using any one of the available risk assessment tools (Box). Understand, however, that no single tool has been shown to be more effective than others.

Although patients and some clinicians tend to overvalue the benefits of chronic opioid therapy, many do not fully appreciate the risks (eg, respiratory depression and death), which can be exacerbated if the patient is using other substance that suppress respiration (eg, benzodiazepines, alcohol, and illicit substances). Written informed consent and treatment agreement is highly recommended; components of such a document are listed in Table 3.²³

Develop a treatment plan that emphasizes functional goals based on the patient’s physical limitations and that incorporates some type of daily, atraumatic physical activity. This plan should be documented and reviewed regularly to help monitor treatment effectiveness.

After an initial trial of a few weeks, the patient and clinician should meet to review the 5 “A”s (Table 4)²⁴ to determine the success of the opioid regimen. Consulting your state’s prescription drug monitoring program (if one is available), obtaining a random urine drug test, and doing a pill count can provide useful, objective data. If the patient has not made progress but has experienced no adverse effects, then a small dosage increase might be warranted. If any of the 5 “A”s indicates lack of improvement or increased risk, consider stopping opioid therapy and exploring non-opioid options to manage chronic pain.

Referrals to a pain specialist or an addiction specialist, or both, might be needed, depending on the patient’s condition at any given follow-up visit. Such referral decisions, as well as all treatment plans, should be documented clearly in the medical record to prevent any misunderstanding, false accusations, or medicolegal repercussions regarding the rationale for continuing or terminating opioid-based treatment.

Non-pharmaceutical therapy for treating pain
The pain management field has successfully integrated the biopsychosocial model into regular practice. This model advocates the use of multimodal non-drug interventions in conjunction with opioid and non-opioid medications. Such interventions address behavioral, cognitive, sociocultural (psychosocial), lifestyle, and physiological dimensions of pain. A partial list of non-drug interventions is provided in Table 5.