Knowledge – Pain

  1. Introduction of Pain
    1. Definition and Classification    More details…
    2. Social Impact of Pain    More details…
    3. Principle of making an accurate pain diagnosis    More details…
    4. Principle of pain management    More details…
  2. Important checklist for your pain care    More details…
  3. Pain Medications
    1. Nonopioid analgesics    More details…
      Opioid analgesics    More details…
    2. Coanaglesics    More details…
  4. Common Pain Procedures    More details…

Introduction of Pain – Definition and Classification

        1. Nociceptive pain: originates from the damaging tissues other than peripheral and central nervous system, such as joint pain and muscular pain.
        2. Neuropathic pain: originates from injury to the nervous system, in the absence of noxious stimulation, such as trigeminal nerve pain, diabetic
            neuropathic pain, etc.
        3. Mixed type of above: Such as lower back pain and cancer pain.

Introduction of PainSocial Impact of Pain

1.  30% of the population of developed countries suffered from chronic pain

2.  In United States:

(1) 70 million people report chronic pain
(2) 31 million people have chronic lower back pain
(3) 20-50 million people suffer arthritis
(4)70-80% of the population suffers from head pain at least once per month

Introduction of Pain – Principle of Making an Accurate Pain Diagnosis

  1. Obtain a detail and thorough pain history.
  2. Complete a meaningful physical exam that may apply skills in physical medicine and rehabilitation, sports medicine, neurology and physical therapy.
  3. Make a list of differential diagnosis and the presumably primary diagnosis.
  4. Complete the necessary laboratory and imaging investigations.
  5. Confirm the diagnosis.
  6. Allow enough time for patients to ask questions

Pain – Introduction of Pain – Principle of Pain Management

  1. Review the treatment plan to patients, after confirming the correct diagnosis.
  2. Make sure patients fully understand and allow time for patients to ask questions.
  3. Review history, physical exam and treatment result with patients in each follow-up visit, make sure patients comply to the treatment plan
  4. Always consider multidisciplinary approaches for the comprehensive treatment of pain, including complementary medicine such as acupuncture and herbal medicine.
  5. Nerve use opioid alone, without combining other classes of analgesics such as NSAIDS and coanalgesics (refer to section of pain medication).
  6. Consider a consent with those patients who need long-term opioid use.
  7. If treatment options are exhausted, consider referral to the appropriate pain specialist who may has more knowledge in that related field.

Important checklist for your pain care

  1. Make sure the pain doctor spend enough time to listen to your pain story.  Because you pay for the service, it is your right to request the full time slot you suppose to have with the practitioner, if the pain history is too complicate and the time is not enough, make another appointment.
  2. Make sure your doctor has done the necessary physical exam before giving you the most possibly accurate diagnosis.  You can request a brief exam in each follow-up visit to ensure the diagnosis is still the same and correct.
  3. When the diagnosis is unclear, you can request some symptomatic treatment while waiting for more investigations.
  4. Common investigations in pain management include X-ray, CT, MRI, nerve conductive velocity (NCV) and electromyography (EMG).
  5. Make sure your doctor really knows your pain and give you a tentative plan for your treatment at the end of the visit.
  6. If a reasonable time (4-6 weeks) is given, and your doctor is still not sure of your diagnosis, request a referral for the second opinion. A doctor cannot know anything, but it is always right to refer patients to the specialists who may know how to treat.
  7. If one medication can solve the problem, avoid the second one.  Give yourself enough time to try on the medication before considering adding or switching to another medication.
  8. Comply to the treatment plan, if you have puzzles, always call your doctor.
  9. Report to your doctor and discuss any possible modification if no improvement after 2-4 weeks of treatment.
  10. Ask your doctor to review the medication regiment after 2-3 months of treatment, some medications may no longer be needed after the acute symptoms are under control.  Always alert yourself that almost all the medications have some side effect.
  11. Reasonable office or operating-room interventions can often abort the pain immediately; this can “buy” time for the medications to kick in.
  12. Consider complementary or alternative medicine such as acupuncture, herbal medicine if necessary.  Acupuncture has both laboratory and clinic data to support its use in pain management.  Please visit our acupuncture section for more information.
  13. A comprehensive treatment program is always the best.  This program should include pain specialists in anesthesiology/neurology/physical medicine and rehabilitation, pain psychology, pharmacy, physical therapy, alternative medicine (acupuncture, herb, nutrition, biofeedback, mediation or breathing exercise).
  14. Make sure you have been given necessary or enough visits for the diagnostic or treatment follow-up.
  15. If you are labeled as psychological pain sufferer and you don’t think you are, request a second opinion or explain it to the pain psychologist.  An experienced pain specialist maybe able to find out the “real” organic cause(s).
  16. No patient is entitled to suffer the under-treated pain. You are always right and responsible to look for the best treatment option.
  17. Be optimistic, and always have a hope to solve or relieve the pain.
  18. In most of the situations, consider the nonsteroidal anti-inflammatory drugs (NSAIDS) as the first-line treatment.

Pain MedicationsNonopioid Analgesics

        Drug therapy is the mainstay of management of acute and chronic pain, including cancer pain.  The common pain medications can be classified into
three categories: 1) Nonopioid analgesics; 2) opioid analgesics; 3) coanalgesics.
Nonopioid analgesics
      1. Acetaminophen /Tylenol
        (1) Mechanism: possible inhibitor of cyclooxygenase (COX)-3 in the central
              nervous system
        (2) Advantage: does not affect bleeding, platelet aggregation and stomach mucosal
              integrity. Safe and may be first-line drug for elderly group.
        (3) Caution: limited to < 4 g per day.  No anti-inflammatory effect. Report of over-
              anticagulation with warfarin / coumadin.
      2. Salicylates
        (1) Acetylsalicylic acid / Aspirin
             i.  Mechanism: inhibition of prostaglandin synthesis producing analgesic, anti-
                 inflammatory, antipyretic effects.
             Ii.  Advantage: cardiac protection, thromboembolic prophylaxis, stroke
                  prevention. Less used for pain nowadays
             Iii. Caution: gastric disturbances and prolongation of bleeding time.
                  Salts / Choline magnesium trisalicylate, trilisate
        (2) Salts / Choline magnesium trisalicylate, trilisate
              i.   Mechanism: same as above
              Ii.  Advantage: does not affect the platelet aggregation and bleeding time
              Iii. Caution: gastric irritation.
      3.  Nonsteroidal anti-inflammatory drugs (NSAIDS)
        (1) Non-selective NSAIDS
              i.  Mechanism: inhibition of both COX-1 and COX-2 pathway, centrally and
                  peripherally, and thus production of prostaglandin.
              Ii. Advantage: first line drug in nociceptive pain such as musculo-skeletal pain
                  and cancer pain.  Rich in clinical experience.
              iii. Caution: reversible increase of bleeding time or inhibition of platelet
                   aggregation, inhibition of renal effects.
              Iv. Common drugs
Ibuprofen (Motrin): high incidence of GI and CNS side effects.
Naproxen (Naprosyn, Aleve)
Ketoprofen (Orudis)
Indomethacin (Indocin, Indocin SR)
Sulindac (Clinoril)
Etodolac (Lodine)
Ketorolac (Toradol): limit treatment to 5 days
Diclofenac (Cataflam)
Meloxicam (Mobic)
Piroxicam (Feldene)
Nabumetone (Relafen): fewer GI side effects
        (2) COX-2 selective NSAIDS
i.  Mechanism: selective inhibition of COX-2, but not COX-1 pathway.
Ii. Advantage:
1. Sparing the COX-1 effect provide the safety advantage to GI mucosal integrity and platelet aggregation function / bleeding time.
2. First line drugs for chronic pain such as rheumatoid arthritis, osteoarthritis, juvenile chronic arthritis.
3. First line drugs for mild-to-moderate acute and intermittent pain including cancer pain and pain in elderly group.
4. Adjuvant drug for severe pain.
5. Short-term or intermittent use in patients with bleeding disorders or high risk of peptic ulcer disease (> 65 yr old, prior GI bleeding
6. Used perioperatively, and in situations in which bleeding is concern.
iii. Caution: no safer than non-selective NSAIDS in kidney toxicity.
Iv. Common drugs
Celecoxib (Celebrex): safer for chronic use ( > 6 weeks)
Rofecoxib (Vioxx): for sulfa-allergic patients, longer T1/2
Valdecoxib (Bextra): probably more potent for acute pain
Parecoxib: will be in USA market this fall, prodrug of valdecoxib, for the parenteral use.

Pain MedicationsOpioid Analgesics

Opioid analgesics
      1. Mechanism: binding to specific receptors or the Mu and Kappa types in the central and peripheral nervous system.
      2. Advantage: control of acute and severe pain; control of chronic pain including cancer pain and pain from sickle cell disease, with addition of nonopioids to the regiment.
      3. Caution:
Should only be used as a drug in the multidisciplinary treatment plan and not be used alone
Limit the use meperidine (Demerol, Pethidine) due to the risk of neurotoxicity.
Limit the use of mixed agonist-antagonists (especially Pentazocine / Talwin), due to the psychotomimetic effects.
d. Development of tolerance to: especially the first few days or weeks.
i.   Tolerance to analgesia
ii.  Tolerance to opioid-induced respiratory depression, somnolence, and nausea.
iii. Tolerance to opioid-induced constipation does not occur, and necessitates the use of stimulating laxatives along with chronic opioid therapy
iv. Development of physical dependence: withdrawn symptoms will occur if opioid is abruptly stopped.
1. Opioid abstinence symptoms: anxiety, irritability, chills alternating with hot flashes, salivation, watery eyes, running nose, over-
sweating, nausea, vomiting, abdominal cramps, diarrhea, and insomnia.
2. Appears from hours to days after cessation, depending on the half life of the drug.
Do not confuse physical dependence with opioid addiction: addiction is a drug seeking behavior, commonly involving selling and buying drugs on the street.
f.  Monitor the psychological state of the patient
i.  Patients appear to calm when the pain is well controlled
Ii. Patients appear anxious when the pain is not controlled.
g. Recognize and treat the side effects: sedation, constipation, nausea, vomiting, itching, and respiratory depression
i. Strategies:
1. Decrease the dose and increase the drug interval
2. Try a different opioid
3. Consider multidrug and multimodal therapy
4. Add another drug that counteracts the adverse effect
5. Change the way of giving the medication
      4.   Common drugs:
(1) Morphine-like agonists (mu agonists)
Morphine (MSIR, MS Contin, Oramorph SR, Kadian, Avinza)
Oxycodone (OxyContin)
Oxymorphone (Numorphan): Rectal suppository available
Meperidine (Demerol): neurotoxicity side effect, avoid in children
Propoxyphene (Darvon)
Hydromorphone (Dilaudid)
Fentanyl: (Duragesic-transdermal, Actiq-oral transmucosal)
Levorphanol (Levo-Dromoran)
(2) Weak mu agonist-monoamine reuptake inhibitor
Tramadol (Ultram): lowers seizure threshold
Ultracet (Acetaminophen / Ultram)
(3) Mixed agonist-antagonist (kappa agonists): limited use due to serious psychotomimetic side effect
Pentazocine (Talwin):
Nalbuphine (Nubain): nasal spray available
Butorphanol (Stadol): nasal spray available
(4) Partial agonist:
Buprenorphine (Buprenex): avoid in labor
      5. The way of administration:
Oral transmucosal
Oral transmu
Rectal suppository
Subcutaneous infusion
Intravenous infusion (including PCA)
Intramuscular injection
Epidural infusion
Intrathecal infusion

Pain MedicationsCoanaglesics

  1. Tricyclic antidepressants
    1. Mechanism: Norepinephrine and serotonin reuptake inhibitor.  Enhancement of descending pain inhibitory function.
    2. Advantage: First line for neuropathic pain, enhancing the effects of opioids or NSAIDS, may be used in children with cancer-related pain.
    3. Caution:
      1. Nocturnal orthostatic hypotension
      2. Sedation
      3. Dry eye and dry mouth
      4. Worsening ventricular arrhythmias (contraindicated in coronary disease)
    4. Common drugs
      1. Amitriptyline (Elavil): probably most potent in TCA
      2. Desipramine (Norpramin): least sedation
      3. Nortriptyline (Pamelor): fewer side effects
      4. Imipramine (Tofranil): potent and fewer side effects
  2. Antiepileptic drugs
    1. Proposed mechanism:
      1. Inhibition of ectopic, spontaneous firing of sensory neurons
      2. Inhibition of glutamate transmission or glutamate receptors
      3. Enhancement of GABA inhibitory function.
    2. Advantage: important option for neuropathic pain, especially used for patients who cannot tolerate TCAs, and the pain shooting in quality.
    3. Caution: various, such as sedation, extremity tingling and numbness.
    4. Common drugs
      1. Gabapentin (Neurontin): Best studied and best tolerance.  Probably the most commonly used AED for neuropathic pain
      2. Phenytoin (Dilantin)
      3. Carbamazepine (Tegretol)
      4. Oxycarbazapine (Trileptal)
      5. Topiramate (Topamax)
      6. Valproic acid / sodium valproate (depakote, depacon)
      7. Tiagabine (Gabitril)
      8. Levetiracetam (Keppra)
      9. Lamotrigine (Lamictal)
      10. Zonisimade (Zonegran)
  3. Local anesthetics
    1. Mechanism: stabilizing sensory neuronal membrane
    2. Advantage: topical dermal anesthesia
    3. Caution: not used in infected area
    4. Common drugs
      1. Lidocaine 5% patches (Lidoderm): FDA-approved for postherpetic neuralgia
      2. EMLA cream: mixture of local lidocaine and prilocaine
  4. Glucocorticoids
    1. Proposed mechanism: Immunosuppression and anti-inflammatory action.
    2. Advantage:
      1. Manage acute and chronic cancer pain
        1. Directly lyse lymphoma
        2. Manage malignant lesions of the brachial or lumbosacral plexus when opioid is ineffective
        3. Ameliorate nerve pain by reducing edema in tumor and nervous tissue
      2. Emergent treatment of suspected spinal cord compression.
    3. Caution in chronic use: weight gain, osteoporosis, Cushing’s syndrome, proximal myopathy, psychosis, risk of GI bleeding, infection
    4. Common drugs:
      1. Prednisone
      2. Dexamethasone (Decadron)
  5. Skeletal muscle relaxants
    1. Mechanism: various.  GABA enhancing, central alpha-2 stimulation, etc.
    2. Advantage: useful adjuncts to analgesics for temporary relief of pain secondary to acute muscle injury
    3. Caution: dependence with chronic use, drowsiness
    4. Common drugs
      1. Tizanidine (Zanaflex)
      2. Baclofen: analgesic effect, independent of muscle relaxation
      3. Flexeril
      4. Soma: high addictive potential, limited use
  6. Antihistamines
    1. Mechanism: anti-histamine effect
    2. Advantage: sleep aids and counteract itching from opioid
    3. Caution: weight gain with chronic use
    4. Common drugs
      1. Hydroxyzine (Vistaril, Atarax)
      2. Benadryl
  7. Benzodiazepines
    1. Mechanism: binds to benzodiazepine receptor and enhance GABA inhibitory effect
    2. Advantage: anti-anxiety, sleep aids, anti-convulsion, muscle relaxation
    3. Caution: sedation, increase of depression
    4. Common drugs
      1. Diazepam (Valium)
      2. Lorazepam (Ativan): immediate and short-life effect
      3. Clonazepam (Klonopin)
  8. Caffeine
    1. Proposed mechanism: Antagonizes adenosine A1 and A2 receptors
    2. Advantage: for chronic cancer pain in children
    3. Caution: rebound pain with chronic use
    4. Common drugs
      1. Caffeine citrate
      2. Cafergot (Caffeine / ergotamine)
  9. Topical agents
    1. Mechanism: various.  Capsaicin depletes the substance P from the primary afferent nerve ending; Others increase local blood supply and produce a
    2. feeling of warmth.
    3. Advantage: temporary relief of local pain
    4. Caution: local irritation.
    5. Common drugs:
      1. Capsaicin
      2. Topical analgesic balms (menthol, camphor, methyl salicylate)
  10. Dextroamphetamine
    1. Mechanism: Central stimulation as a sympathomimetic amine
    2. Advantage: counteract the opioid sedation
    3. Caution: psychosis, tachycardia, tremor
  11. Phenothiazines
    1. Mechanism: anti-dopamine effect
    2. Advantage: reducing nausea and vomiting
    3. Caution: restless; tardive dyskinesia with prolonged use
    4. Common drugs:
      1. Prochlorperazine (Compazine)
      2. Chlorpromazine (Thorazine)
      3. Metoclopramide (Reglan)
  12. Bisphosphates
    1. Mechanism: inhibits osteoclastic bone resorption
    2. Advantage: reduces metastatic bone pain and skeletal complication such as pathological fracture in patient with breast cancer and multiple myeloma.
    3. Caution: infusion site reaction, hypocalcemia
    4. Common Drugs
      1. Pamidronate disodium (Aredia)
      2. Zoledronate (Zometa)

Common Pain Procedures

Pain procedure provides a quick relief of acute or exacerbated pain.  Due to the relative short half-life of local anesthetics and even steroid, the pain-
relief effect is generally short-term.  It is very important to combine rationale medications with the invasive intervention in order to maximize and prolong the
analgesic effect.  Our center currently focuses on relatively less-invasive office pain procedures.  Occasionally, patients will be referred to anesthesia pain
specialists for more invasive interventions.  The procedures that will be performed in our center include but not limit to:
      1. Local injection
        i. Trigger point injection
             1. Muscle
             2. Fascia
             3. Tendon
             4. Cyst and ganglion
             5. Bursa
             6. Para-facet
ii. Joint injection and aspiration
      2.  Peripheral nerve block
            a. Greater and lesser occipital nerve
            b. Trigeminal nerve
            c. Lateral femoral cutaneous nerve
            d. Trigeminal nerve
            e. Sciatic nerve
            f. Intercostal nerve
            g. Median nerve
            h. Other nerves
      3.  Plexus block
            a. Superficial cervical plexus
      4.  Epidural anesthetic injection
            a. Caudal
            b. Lumbar
5.  Botulinum toxin-A injection