Best Dx/Best Rx: Pain

Pain

Anne Louise Oaklander, MD, PhD
Massachusetts General Hospital, Harvard Medical School, Boston, MA

Definition/Key Clinical Features
Best Tests
Best Therapy
Best References

Definition/Key Clinical Features

Pain is the cardinal sign of injury and illness and the most common reason to seek medical care
Chronic pain is significantly undertreated
Knowledge and standards of medical care lag behind most of internal medicine
Identifying the cause of pain is the foundation for treatment

Best Tests

History of Chronic Pain

Onset (duration, precipitant, lag between precipitant and onset of pain)
Progression (improving, worsening, static)
Location
Pain qualities (constant or intermittent, detailed features)
What makes it better or worse
Response to previous treatments tried
Intensity (0–10 Likert scale for adults, Faces Pain Scale for children)
Effects of pain (functioning, disability, depression, anxiety)
Patient's expectations for evaluation

Standard Past Medical History

Prior trauma to area, even if minor
Illnesses associated with chronic pain
Activities that can cause chronic pain through overuse, misuse
Psychiatric or social issues that impair coping ability
History of substance abuse

Comprehensive Examination

First examination should look for standard cause of pain (tissue injury or illness)
Evidence of rheumatologic disorder
Evidence of neurologic disorder (localization corresponding to nerve or nerve root, accompanying sensory abnormalities)

Diagnostic Evaluation

First tests should look for standard cause of pain (tissue injury or illness)
Consider need for specialist referral
Consider rheumatologic consultation for widespread or joint pain
Consider neurologic consultation for neuropathic or otherwise unexplained pain

Best Therapy*

Best Treatment Principles

The best treatment is to eliminate the cause of pain
Consider lifestyle changes (e.g., weight loss to treat diabetic neuropathy)
Consider definitive treatment of disease rather than pain palliation

Identify treatable comorbidities (e.g., poor sleep, depression)
Support healing (e.g., improve oxygenation by smoking cessation)
Aim for functional restoration, not just pain relief

Best Medical Treatment for Inflammatory/Nociceptive Pain (Acute or Chronic)

NSAIDS, aspirin, or acetaminophen; best initial treatment

Can be inadvertently overdosed because viewed as innocuous and present in combination medications, including over-the-counter drugs, so calculate total daily dose
Acetaminophen can cause liver failure
Ibuprofen and naproxen can cause gastrointestinal irritation, including bleeding, renal dysfunction, and tinnitus

Opioids; the standard of care for moderate to severe pain
- Numerous forms with varied routes of administration, duration of effect
- Respiratory depression is major adverse effect of rapid administration, sedation, constipation with oral use
- Must consider potential for misuse
- Minimize tolerance by avoiding dose escalation
- Morphine stands out for global availability, low cost, varied administration routes
- Methadone stands out for long duration, low cost, low-dose pills

Best Interventional Treatment Options for Inflammatory/Nociceptive Neuropathic Pain

Local anesthetic and/or corticosteroid blockade of neural structures useful mostly for acute but not chronic pain
Terminal patients may benefit substantially from prolonged neural blockade and ablative neurosurgical procedures

Best Medical Treatment Options for Neuropathic Pain

Tricyclics are unsurpassed for efficacy; some side effects (sleep, antidepressant) are beneficial

Nortriptyline and desipramine have fewest adverse effects; amitriptyline has most; avoid if possible
Start at 25 mg in evening (10 mg for elderly); increase as tolerated
Usual adult dose: at least 50–75 mg daily
Relative contraindications include prior myocardial infarction, arrhythmia, narrow-angle glaucoma, constipation, hypotension, urinary retention
Available as generic

Gabapentin; second choice for neuropathic pain in the young and healthy, first choice when tricyclics contraindicated

Major side effects: sedation, peripheral edema
Usual adult dose: at least 1,800 mg/day, dosed t.i.d.
Available as generic

Pregabalin; second-choice treatment (recent to market, no generics) for various neuropathic pains

Usual adult dose: 150–600 mg
Only clear benefit over gabapentin is b.i.d. dosing

Duloxetine; second-choice treatment (recent to market, no generics) for various neuropathic pains

Usual adult dose: 30–90 mg/day

Carbamazepine; first-choice treatment for trigeminal neuralgia, third-choice option for other neuropathic pain conditions

Usual adult dose: at least 400–1200 mg/day
Available as generic
Common side effects: cognitive, diplopic
Serious side effects: monitor for hyponatremia, liver damage, and bone marrow suppression

Opioids; third-choice option for neuropathic pain, second choice in elderly as tricyclics poorly tolerated, less risk of misuse

Tramadol and methadone stand out for multiple modes of action

Best Topical Treatment Options for Neuropathic Pain

Local anesthetics in various formulations applied under occlusion for penetration; lidoderm patch 5% and other forms available as generics

Best Surgical/Interventional Treatment Options for Neuropathic Pain

For cases refractory to best medical management, evaluate if needed for neural decompression and consider neuromodulation, starting with less invasive modalities

Best References

Chou R, Fanciullo GJ, Fine PG, et al: J Pain 10:113–30, 2009 [PMID 19187889]

American Geriatrics Society: J Am Geriatr Soc 57:1331–46, 2009 [PMID 19573219]

Attal N, Cruccu G, Baron R, et al: Eur J Neurol 17:1113–e88, 2010 [PMID 20402746]

Chapman CR, Lipschitz DL, Angst MS, et al: J Pain 11:807–29, 2010 [PMID 20430701]

Chou R, Atlas SJ, Stanos SP, Rosenquist RW: Spine 34(10):1078–93, 2009 [PMID 19363456]

* To obtain additional drug information, click on the DrugInfo tab in the left column, or click on the following link: http://search.medscape.com/drug-reference-search?queryText=

The author is a member of the speakers' bureaus of Pfizer/Pharmacia, GlaxoSmithKline, and Ortho-McNeil Pharmaceutical, Inc.

January 2011