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Chronic Pain Management: An Evidence-Based Approach

Basics

  • Chronic pain: pain >3 months beyond normal healing.
  • CNS neuroplasticity causes emotional, psychological, cognitive pain aspects.
  • Undertreatment and opioid misuse are concurrent epidemics.
  • People of color, especially African Americans, often undertreated.
  • Opioids reserved for indicated chronic nonmalignant pain, prescribed carefully.

Epidemiology

  • 20-40% primary care patients report chronic pain.
  • Annual U.S. economic cost: $560-635 billion.
  • Higher prevalence in women and lower socioeconomic groups.

Etiology and Pathophysiology

  • Repeated/prolonged tissue injury lowers nociceptive threshold → peripheral/central sensitization.
  • Brain areas (amygdala, prefrontal cortex) remodel with chronic pain.
  • Pain severity may exceed observable tissue damage.
  • Genetics: opioid receptor polymorphisms influence opioid response.

Risk Factors

  • Trauma (MVAs, repetitive injuries, falls).
  • Postsurgical states (back surgeries, amputations).
  • Psychiatric comorbidities: substance abuse, depression, PTSD.

General Prevention

  • Ergonomic workplace design.
  • Varicella vaccination and rapid shingles treatment to prevent postherpetic neuralgia.
  • Tight glycemic control in diabetes.
  • Smoking cessation and alcohol abuse prevention.

Commonly Associated Conditions

  • Any chronic disease or its treatments.

Diagnosis

Pain Types

  • Nociceptive: somatic (sharp, localized), visceral (dull, poorly localized).
  • Neuropathic: burning, tingling, numbness.
  • Sympathetically mediated (e.g., complex regional pain syndrome).

History

  • Detailed pain characterization (location, intensity, quality, triggers).
  • Functional impact and quality of life assessment.
  • Substance abuse, mental health, and abuse history screening.
  • Use standardized tools: Brief Pain Inventory, PHQ-9, SOAPP.

Physical Exam

  • Functional and behavioral assessment guided by history.

Differential Diagnosis

  • Consider pseudoaddiction, opioid tolerance, opioid-induced hyperalgesia, substance use disorder, diversion.

Diagnostic Tests

  • Urine drug screens: immunoassays (morphine/heroin detection), chromatography for specifics.
  • Consider interventional pain clinic for nerve blocks or injections.

Treatment

Goals

  • Restore function and reduce pain.

General Measures

  • Pain and function diaries.
  • Multimodal approaches: exercise, CBT, education, yoga, massage, relaxation, mindfulness, acupuncture.
  • Sympathetic blocks for complex regional pain syndrome.
  • Cannabis use remains controversial with low-quality evidence.

Medication

Mild to Moderate Noncancer Pain

  • Acetaminophen (max 4 g/day in healthy adults; 2 g in elderly with hepatic disease/alcohol use).
  • NSAIDs with caution; COX-2 inhibitors may have cardiac risk.
  • Topicals: NSAIDs (diclofenac), lidocaine, ketamine, capsaicin.
  • Tramadol for neuropathic pain; dose adjustment needed; risk of seizures.

Neuropathic Pain

  • TCAs: desipramine, nortriptyline (start low in elderly).
  • SNRIs: duloxetine.
  • Anticonvulsants: gabapentin, pregabalin.
  • Opioids last line.

Moderate to Severe Pain

  • Opioids: morphine, oxycodone, hydromorphone, fentanyl, oxymorphone.
  • Avoid morphine in renal insufficiency.
  • Methadone requires expertise due to interactions and arrhythmia risk.
  • Buprenorphine may be effective, especially without opioid use disorder history.
  • Use sustained-release opioids for chronic pain; short-acting for breakthrough pain.
  • Common side effects: constipation (use senna), nausea, sedation, pruritus.
  • Coprescribe naloxone nasal spray.

Precautions

  • Universal precautions mandatory for opioid prescribing.
  • Monitor for abuse, diversion, and side effects.

Surgery/Procedures

  • Consider nerve blocks, joint injections, spinal cord stimulation, intrathecal meds as appropriate.

Complementary & Alternative Medicine

  • Mindfulness-based stress reduction and CBT for chronic low back pain.
  • Yoga as effective as physical therapy for moderate-severe low back pain.

Ongoing Care

Follow-up

  • Nonjudgmental approach.
  • Monitor pain, function, quality of life, benefits, and risks.
  • Urine drug screens and prescription monitoring programs.
  • Taper/discontinue meds if no benefit or abuse detected.
  • Shared decision-making for opioid tapering.

Naloxone Kit

  • Two 1 mg/mL intranasal sprays; onset 2-5 minutes, duration 30-90 minutes.

Patient Education

  • American Chronic Pain Association: https://theacpa.org

Complications

  • Addiction rate 3-19%; aberrant behaviors 5-24%.
  • Definitions:
  • Addiction: compulsive drug use despite harm.
  • Physical dependence: withdrawal symptoms on cessation.
  • Tolerance: diminished drug effect over time.
  • Diversion: unauthorized distribution of medications.

Clinical Pearls:

  • Validate the patient's pain as real.
  • Pain-free life may not be possible; aim for improved function and quality of life.
  • Use multidisciplinary approach combining nonpharmacologic and pharmacologic therapies.
  • Follow universal precautions for opioid prescribing.