Pain medical therapy

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Medical Therapy

Clinical practice guidelines[1] based on systematic reviews[2][3] address medical therapy.

The Cochrane Collaboration provides additional systematic reviews[4].


Anesthesia is the condition of having the feeling of pain and other sensations blocked by drugs that induces a lack of awareness. It may be a total or a minimal lack of awareness throughout the body (i.e. general anesthesia), or a lack of awareness in a part of the body (i.e. regional or local anesthesia).


Analgesia is an alteration of the sense of pain without loss of consciousness. The body possesses an endogenous analgesia system, which can be supplemented with painkillers or analgesic drugs to regulate nociception and pain. Analgesia may occur in the central nervous system or in peripheral nerves and nociceptors. The perception of pain can also be modified by the body according to the gate control theory of pain.

The endogenous central analgesia system is mediated by 3 major components : the periaquaductal grey matter, the nucleus raphe magnusand the nociception inhibitory neurons within the dorsal horns of the spinal cord, which act to inhibit nociception-transmitting neurons also located in the spinal dorsal horn. The peripheral regulation consists of several different types of opioid receptors that are activated in response to the binding of the body's endorphins. These receptors, which exist in a variety of areas in the body, inhibit firing of neurons that would otherwise be stimulated to do so by nociceptors.

The gate control theory of pain postulates that nociception is "gated" by non-noxious stimuli such as vibration. Thus, rubbing a bumped knee seems to relieve pain by preventing its transmission to the brain. Pain is also "gated" by signals that descend from the brain to the spinal cord to suppress (and in other cases enhance) incoming nociceptive information.

Complementary and Alternative Medicine

A survey of American adults found pain was the most common reason that people use complementary and alternative medicine.

Traditional Chinese medicine views pain as a 'blocked' qi, akin to electrical resistance, with treatments such as acupunctureclaimed as more effective for nontraumatic pain than traumatic pain. Although the mechanism is not fully understood, acupuncture may stimulate the release of large quantities of endogenous opioids.[5]

Pain treatment may be sought through the use of nutritional supplements such as curcumin, glucosamine, chondroitin,bromelain andomega-3 fatty acids.

Hypnosis as well as diverse perceptional techniques provoking altered states of consciousness have proven to be of important help in the management of all types of pain.[6]

Some kinds of physical manipulation or exercise are showing interesting results as well.[7]

Chili Peppers, Capsaicin, and Pain

The hot feeling, red face, and watery eyes you experience when you bite into a red chili pepper may make you reach for a cold drink, but that reaction has also given scientists important information about pain. The chemical found in chili peppers that causes those feelings is capsaicin (pronounced cap-SAY-sin), and it works its unique magic by grabbing onto receptors scattered along the surface of sensitive nerve cells in the mouth.

In 1997, scientists at the University of California at San Francisco discovered a gene for a capsaicin receptor, called the vanilloid receptor. Once in contact with capsaicin, vanilloid receptors open and pain signals are sent from the peripheral nociceptor and through central nervous system circuits to the brain. Investigators have also learned that this receptor plays a role in the burning type of pain commonly associated with heat, such as the kind you experience when you touch your finger to a hot stove. The vanilloid receptor functions as a sort of "ouch gateway," enabling us to detect burning hot pain, whether it originates from a 3-alarm habanera chili or from a stove burner.

Capsaicin is currently available as a prescription or over-the-counter cream for the treatment of a number of pain conditions, such as shingles. It works by reducing the amount of substance P found in nerve endings and interferes with the transmission of pain signals to the brain. Individuals can become desensitized to the compound, however, perhaps because of long-term damage to nerve tissue. Some individuals find the burning sensation they experience when using capsaicin cream to be intolerable, especially when they are already suffering from a painful condition, such as postherpetic neuralgia. Soon, however, better treatments that relieve pain by blocking vanilloid receptors may arrive in drugstores.


As a painkiller, marijuana or, by its Latin name, cannabis, continues to remain highly controversial. In the eyes of many individuals campaigning on its behalf, marijuana rightfully belongs with other pain remedies. In fact, for many years, it was sold under highly controlled conditions in cigarette form by the Federal government for just that purpose.

In 2022, a systematic review by the U.S. Agency for Healthcare Research and Quality concluded, "Oral, synthetic cannabis products with high THC-to-CBD ratios and sublingual, extracted cannabis products with comparable THC-to-CBD ratios may be associated with short-term improvements in chronic pain and increased risk for dizziness and sedation[8]."

  • However, the largest randomized controlled trial in the review, the MUSEC trial by Zajicek:
    • The registered outcomes were primary "Change in muscle stiffness: 11-point numerical Likert scale [ Time Frame: 12 weeks ]" and secondary "Change in pain: 11-point numerical Likert scale [ Time Frame: 12 weeks ]" of change on a 0-10 pain scale (registered outcome) [9], but these outcomes of change were not reported.
    • The reported outcomes were rate of stiffness rating of 0 through 3 out of 10 and the same rate for pain.
      • The difference between the registered and reported outcomes raises the question of selecting reporting bias. In addition, the tests of significance used one tail.

In 1997, the National Institutes of Health held a workshop to discuss research on the possible therapeutic uses for smoked marijuana. Panel members from a number of fields reviewed published research and heard presentations from pain experts. The panel members concluded that, because there are too few scientific studies to prove marijuana's therapeutic utility for certain conditions, additional research is needed. There is evidence, however, that receptors to which marijuana binds are found in many brain regions that process information that can produce pain.

Nerve Blocks

Nerve blocks may involve local anesthesia, regional anesthesia or analgesia, or surgery; dentists routinely use them for traditional dental procedures. Nerve blocks can also be used to prevent or even diagnose pain.

In the case of a local nerve block, any one of a number of local anesthetics may be used; the names of these compounds, such as lidocaine or novocaine, usually have an aine ending. Regional blocks affect a larger area of the body. Nerve blocks may also take the form of what is commonly called an epidural, in which a drug is administered into the space between the spine's protective covering (the dura) and the spinal column. This procedure is most well known for its use during childbirth. Morphine and methadone are opioid narcotics (such drugs end in ine or one) that are sometimes used for regional analgesia and are administered as an injection.

Neurolytic blocks employ injection of chemical agents such as alcohol, phenol, or glycerol to block pain messages and are most often used to treat cancer pain or to block pain in the cranial nerves. In some cases, a drug called guanethidine is administered intravenously in order to accomplish the block.

Surgical blocks are performed on cranial, peripheral, or sympathetic nerves. They are most often done to relieve the pain of cancer and extreme facial pain, such as that experienced with trigeminal neuralgia. There are several different types of surgical nerve blocks and they are not without problems and complications. Nerve blocks can cause muscle paralysis and, in many cases, result in at least partial numbness. For that reason, the procedure should be reserved for a select group of patients and should only be performed by skilled surgeons. Types of surgical nerve blocks include:

  • Neurectomy (including peripheral neurectomy) in which a damaged peripheral nerve is destroyed.
  • Spinal dorsal rhizotomy in which the surgeon cuts the root or rootlets of one or more of the nerves radiating from the spine. Other rhizotomy procedures include cranial rhizotomy and trigeminal rhizotomy, performed as a treatment for extreme facial pain or for the pain of cancer.
  • Sympathectomy, also called sympathetic blockade, in which a drug or an agent such as guanethidine is used to eliminate pain in a specific area (a limb, for example). The procedure is also done for cardiac pain, vascular disease pain, the pain of reflex sympathetic dystrophy syndrome, and other conditions. The term takes its name from the sympathetic nervous system and may involve, for example, cutting a nerve that controls contraction of one or more arteries.


  1. Qaseem A, McLean RM, O'Gurek D, Batur P, Lin K, Kansagara DL (2020). "Nonpharmacologic and Pharmacologic Management of Acute Pain From Non-Low Back, Musculoskeletal Injuries in Adults: A Clinical Guideline From the American College of Physicians and American Academy of Family Physicians". Ann Intern Med. doi:10.7326/M19-3602. PMID 32805126 Check |pmid= value (help).
  2. Busse JW, Sadeghirad B, Oparin Y, Chen E, Goshua A, May C; et al. (2020). "Management of Acute Pain From Non-Low Back Musculoskeletal Injuries : A Systematic Review and Network Meta-analysis of Randomized Trials". Ann Intern Med. doi:10.7326/M19-3601. PMID 32805127 Check |pmid= value (help).
  3. Riva JJ, Noor ST, Wang L, Ashoorion V, Foroutan F, Sadeghirad B; et al. (2020). "Predictors of Prolonged Opioid Use After Initial Prescription for Acute Musculoskeletal Injuries in Adults : A Systematic Review and Meta-analysis of Observational Studies". Ann Intern Med. doi:10.7326/M19-3600. PMID 32805130 Check |pmid= value (help).
  4. Jones P, Lamdin R, Dalziel SR (2020). "Oral non-steroidal anti-inflammatory drugs versus other oral analgesic agents for acute soft tissue injury". Cochrane Database Syst Rev. 8: CD007789. doi:10.1002/14651858.CD007789.pub3. PMC 7438775 Check |pmc= value (help). PMID 32797734 Check |pmid= value (help).
  5. Sapolsky, Robert M. (1998). Why zebras don't get ulcers: An updated guide to stress, stress-related diseases, and coping. New York: W.H. Freeman and CO. ISBN 0-585-36037-5.
  6. Robert Ornstein PhD, David Sobel MD (1988). The Healing Brain. New York: Simon & Schuster Inc. pp. 98–99. ISBN 0-671-66236-8.
  7. Douglas E DeGood, Donald C Manning MD, Susan J Middaugh (1997). The headache & Neck Pain Workbook. Oakland, California: New Harbinger Publications. ISBN 1-57224-086-5.
  8. McDonagh MS, Morasco BJ, Wagner J, Ahmed AY, Fu R, Kansagara D; et al. (2022). "Cannabis-Based Products for Chronic Pain : A Systematic Review". Ann Intern Med. 175 (8): 1143–1153. doi:10.7326/M21-4520. PMID 35667066 Check |pmid= value (help).
  9. MUltiple Sclerosis and Extract of Cannabis (MUSEC) Study (MUSEC). Available at

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