Residency · Residency · Internal Medicine

Chronic Pain Management: A Multimodal Approach

Introduction

Chronic pain, defined as pain persisting beyond 3 months, affects over 50 million US adults and is the leading cause of disability worldwide. The failed paradigm of opioid-centric pain management contributed to an ongoing addiction and overdose crisis. Modern pain management emphasizes a biopsychosocial model with multimodal therapies targeting the physical, psychological, and social dimensions of pain. Internal medicine residents must be comfortable initiating evidence-based non-opioid therapies and managing opioids safely when indicated.

Pain Neuroscience

• Nociceptive pain: caused by tissue damage activating peripheral nociceptors (somatic or visceral)
• Neuropathic pain: caused by lesion or disease of the somatosensory nervous system (burning, shooting, tingling)
• Nociplastic pain (central sensitization): amplified central nervous system processing without clear nociceptive input (fibromyalgia, chronic widespread pain, irritable bowel syndrome)
• Peripheral and central sensitization: repeated nociceptive input leads to reduced pain thresholds, expanded receptive fields, and pain from normally non-painful stimuli (allodynia)
• Identifying the pain mechanism guides pharmacotherapy selection

Assessment

• Pain history: location, quality, intensity (0-10 NRS), temporal pattern, aggravating/alleviating factors, prior treatments
• Functional impact: PEG scale (Pain, Enjoyment of life, General activity); functional goals are more meaningful than pain scores
• Psychosocial assessment: depression, anxiety, catastrophizing, social isolation, adverse childhood experiences
• Screen for substance use disorder: Opioid Risk Tool (ORT), SOAPP-R; urine drug testing
• Red flags: unexplained weight loss, fever, neurologic deficits, progressive weakness (evaluate for malignancy, infection, cauda equina)

Non-Pharmacologic Therapies

Physical and Rehabilitative

• Exercise therapy: strongest evidence base; aerobic exercise, resistance training, yoga, tai chi all reduce pain and improve function in chronic low back pain, osteoarthritis, and fibromyalgia
• Physical therapy: graded exercise programs, manual therapy, activity modification
• Cognitive behavioral therapy (CBT): restructures maladaptive pain beliefs and catastrophizing; NNT of 2-4 for clinically meaningful improvement
• Acceptance and commitment therapy (ACT): emphasizes psychological flexibility and value-based living despite pain
• Mindfulness-based stress reduction (MBSR): demonstrated benefit in chronic low back pain (JAMA 2016)

Interventional Procedures

• Epidural steroid injections: short-term relief for lumbar radiculopathy; limited evidence for long-term benefit
• Facet joint interventions: medial branch blocks followed by radiofrequency ablation for facet-mediated pain
• Spinal cord stimulation: for failed back surgery syndrome and complex regional pain syndrome
• Trigger point injections: for myofascial pain syndrome
• Nerve blocks: peripheral nerve blocks for localized neuropathic pain

Non-Opioid Pharmacotherapy

First-Line Agents by Pain Type

Neuropathic Pain

• Gabapentinoids: gabapentin (300-3600 mg/day), pregabalin (150-600 mg/day); NNT 6-7 for 50% pain relief
• SNRIs: duloxetine (60-120 mg/day), venlafaxine (150-225 mg/day); also effective for comorbid depression
• Tricyclic antidepressants: amitriptyline, nortriptyline (25-150 mg at bedtime); NNT 3-4; anticholinergic side effects limit use in elderly
• Topical lidocaine (5% patch): for localized neuropathic pain, minimal systemic absorption
• Topical capsaicin (8% patch): for postherpetic neuralgia, HIV-associated neuropathy

Musculoskeletal Pain

• Acetaminophen: up to 2 g/day in chronic use (reduced ceiling to protect against hepatotoxicity)
• NSAIDs: use lowest effective dose for shortest duration; topical NSAIDs (diclofenac gel) preferred for localized osteoarthritis (comparable efficacy, fewer systemic effects)
• Duloxetine: FDA-approved for chronic musculoskeletal pain and osteoarthritis
• Cyclobenzaprine: short-term use for acute muscle spasm; avoid chronic use

Nociplastic Pain (Fibromyalgia)

• Duloxetine (60-120 mg/day): FDA-approved for fibromyalgia
• Pregabalin (300-450 mg/day): FDA-approved for fibromyalgia
• Milnacipran (100-200 mg/day): FDA-approved for fibromyalgia
• Low-dose naltrexone (1.5-4.5 mg/day): emerging evidence for fibromyalgia and central sensitization

Opioid Therapy: When and How

Indications

• Moderate-to-severe pain significantly impairing function despite optimized non-opioid multimodal therapy
• Cancer pain, palliative care, and end-of-life care
• Chronic non-cancer pain: opioids should be a last resort, not a first-line therapy

Safe Prescribing Practices (CDC 2022 Guideline)

• Start with immediate-release opioids at lowest effective dose
• Avoid exceeding 50 morphine milligram equivalents (MME)/day without careful reassessment; use extreme caution above 90 MME/day
• Co-prescribe naloxone for all patients receiving >= 50 MME/day, history of overdose, concurrent benzodiazepine use, or substance use disorder history
• Prescription drug monitoring program (PDMP): check before every new opioid prescription and periodically thereafter
• Urine drug testing: baseline and at least annually; confirm expected drug presence and absence of undisclosed substances
• Reassess opioid benefit every 1-3 months; taper if risks outweigh benefits

Opioid Tapering

• Gradual taper: reduce by 10% of total daily dose per month
• Avoid abrupt discontinuation (risk of withdrawal, destabilization, illicit opioid use)
• Optimize non-opioid pain management before and during taper
• Collaborate with addiction medicine if opioid use disorder is identified

Opioid Use Disorder

• Screen for OUD using DSM-5 criteria
• Medication-assisted treatment (MAT): buprenorphine/naloxone or methadone; reduces mortality by 50%
• Internal medicine residents should obtain X-waiver training (now eliminated; all DEA-registered providers can prescribe buprenorphine)

Key Clinical Pearls

• Identify the pain mechanism (nociceptive, neuropathic, or nociplastic) to guide pharmacotherapy selection
• Exercise and CBT have the strongest evidence for chronic pain and should be prescribed alongside pharmacotherapy
• Duloxetine is the most versatile non-opioid analgesic, with FDA approval for neuropathic pain, fibromyalgia, chronic musculoskeletal pain, and osteoarthritis
• All providers with a DEA license can now prescribe buprenorphine for opioid use disorder; there is no longer a separate waiver requirement

References

1. Dowell D, Ragan KR, Jones CM, et al. CDC Clinical Practice Guideline for Prescribing Opioids for Pain -- United States, 2022. MMWR Recomm Rep. 2022;71(3):1-95.
2. Finnerup NB, Attal N, Haroutounian S, et al. Pharmacotherapy for Neuropathic Pain in Adults: A Systematic Review and Meta-Analysis. Lancet Neurol. 2015;14(2):162-173.
3. Cherkin DC, Sherman KJ, Balderson BH, et al. Effect of Mindfulness-Based Stress Reduction vs Cognitive Behavioral Therapy on Back Pain and Functional Limitations. JAMA. 2016;315(12):1240-1249.
4. Volkow ND, Blanco C. The Changing Opioid Crisis: Development, Challenges, and Opportunities. Mol Psychiatry. 2021;26(1):218-233.

For the intern

At 3am, prioritize acute pain crises and safety concerns: evaluate for red flags (fever, neurologic deficits, cauda equina), manage acute exacerbations with non-opioid analgesics first, check the Prescription Drug Monitoring Program (PDMP) before prescribing any controlled substances, and co-prescribe naloxone for patients on ≥50 morphine milligram equivalents per day or with overdose risk factors. Chronic pain optimization—starting gabapentin, referring to physical therapy, initiating Cognitive Behavioral Therapy (CBT)—can wait until morning rounds when you can establish functional goals and coordinate multimodal care.

Common pitfalls

• Chasing pain scores instead of function: A patient reporting 7/10 pain who walks daily and works has better outcomes than someone reporting 5/10 who is bedbound. Use the PEG scale (Pain, Enjoyment, General activity) to set realistic functional goals rather than targeting pain elimination.

• Prescribing long-acting opioids for opioid-naive patients: Always start with immediate-release formulations at the lowest dose. Long-acting opioids dramatically increase overdose risk in patients without established tolerance.

• Overlooking substance use disorder: If a patient meets Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria for opioid use disorder, they need buprenorphine or methadone, not pain management alone. You can now prescribe buprenorphine with your Drug Enforcement Administration (DEA) license—no separate waiver needed.

• Ignoring the psychosocial dimension: Chronic pain without addressing depression, catastrophizing, or adverse childhood experiences leads to treatment failure. Depression screening and mental health referral are essential components of pain management.

Make it stick

Imagine Ms. Davis, a 68-year-old with chronic low back pain and osteoarthritis, who previously received daily hydrocodone. You're covering the inpatient service and she's admitted for community-acquired pneumonia. During rounds, she asks for more pain medication. Instead of simply increasing her opioid dose, you recall the lecture: you assess her pain mechanism (likely nociceptive from OA, maybe some nociplastic overlap if it's widespread), check her function (can she get out of bed?), screen for depression, and note her prior opioid use in the PDMP. You initiate scheduled acetaminophen and topical NSAIDs for her knee OA, encourage gentle mobilization with physical therapy, and suggest a consult for Cognitive Behavioral Therapy upon discharge. This integrated approach, rather than just reaching for the opioid, is the essence of multimodal chronic pain management.

If you remember one thing

Chronic pain management is not just about prescribing pills; it's about understanding the biopsychosocial model and applying multimodal non-opioid therapies first. Always prioritize functional improvement over subjective pain scores when assessing treatment efficacy.

Read this lecture as Markdown