Terra Pharmaceuticals
Definitions and Types of Pain
Defining Pain
Pain is a perception that signals the individual that tissue damage has occurred or may be occurring. It is subjective and very complex. The processes in the body that are involved in the perception of pain are called "nociception."
Classifying Pain
Pain can be "acute" or "chronic." Acute pain lasts a short time, or is expected to be over soon. The time frame may be as brief as seconds or as long as weeks.
Chronic pain may be defined as pain that lasts beyond the healing of an injury, continues for a period of several months or longer, or occurs frequently for at least months.
To develop the best treatment strategies, health care professionals also classify pain based on its characteristics, its cause, or the mechanisms in the body or the mind that are probably involved in sustaining it. One common classification based on mechanisms distinguishes pain into categories called "nociceptive," "neuropathic," and "psychogenic."
Types of Pain
Nociceptive Pain: Nociceptive pain is believed to be caused by the ongoing activation of pain receptors in either the surface or deep tissues of the body. There are two types: "somatic" pain and " visceral" pain.
"Somatic" pain is caused by injury to skin, muscles, bone, joint, and connective tissues. Deep somatic pain is usually described as dull or aching, and localized in one area. Somatic pain from injury to the skin or the tissues just below it often is sharper and may have a burning or pricking quality.
Somatic pain often involves inflammation of injured tissue. Although inflammation is a normal response of the body to injury, and is essential for healing, inflammation that does not disappear with time can result in a chronically painful disease. The joint pain caused by rheumatoid arthritis may be considered an example of this type of somatic nociceptive pain.
"Visceral" pain refers to pain that originates from ongoing injury to the internal organs or the tissues that support them. When the injured tissue is a hollow structure, like the intestine or the gall bladder, the pain often is poorly localized and cramping. When the injured structure is not a hollow organ, the pain may be pressure-like, deep, and stabbing.
Neuropathic Pain: Neuropathic pain is believed to be caused by changes in the nervous system that sustain pain even after an injury heals. In most cases, the injury that starts the pain involves the peripheral nerves or the central nervous system itself. It can be associated with trauma or with many different types of diseases, such as diabetes. There are many neuropathic pain syndromes, such as diabetic neuropathy, trigeminal neuralgia, postherpetic neuralgia ("shingles"), post-stroke pain, and complex regional pain syndromes (also called reflex sympathetic dystrophy or "RSD" and causalgia). Some patients who get neuropathic pain describe it as bizarre, unfamiliar pain, which may be burning or like electricity. The pain may be associated with sensitivity of the skin.
Psychogenic Pain: Most patients with chronic pain have some degree of psychological disturbance. Patients may be anxious or depressed, or have trouble coping. Psychological distress may not only be a consequence of the pain, but may also contribute to the pain itself. "Psychogenic" pain is a simple label for all kinds of pain that can be best explained by psychological problems.
Pain Management
· Anesthesiologic Approaches
· Neurostimulatory Approaches
· Pharmacological Approaches
· Psychological/Mind-Body Therapies
· Rehabilitative Approaches
· Surgical Approaches
Conventional Approaches
Modifying the Underlying Disorder
One of the goals of the pain assessment is to identify the potential causes of the pain. Treatment directed at the cause always should be considered as part of the therapeutic strategy. For example, a drug or nutrient that helps regulate the immune system and reduces the inflammation of rheumatoid arthritis is likely to have positive effects on the pain. Similarly, radiation given to the site of a malignant tumor is likely to relieve pain.
Pharmacological Approaches
There are three broad categories of analgesic drugs:
* nonopioid analgesics
* adjuvant analgesics
* opioid analgesics
Nonopioid Analgesics
The nonopioid analgesics include acetaminophen (also called paracetamol), and the nonsteroidal anti-inflammatory drugs (known as the NSAIDs). The NSAIDs are nonspecific analgesics and can potentially be used for any type of acute or chronic pain. Because they are both analgesic and anti-inflammatory, however, they may be particularly useful for pain related to joint problems and other musculoskeletal disorders (Wallenstein, 2002).
The NSAIDs are a very diverse group of drugs. They all inhibit an enzyme called "cyclo-oxygenase" (COX). COX exists in many tissues and inhibition of this enzyme reduces the amount of chemicals known as "prostaglandins" in these sites. Prostaglandins have many roles, including the production of inflammation. Inhibition of COX by a NSAID, therefore, may reduce pain and inflammation.
There are at least two forms of COX. COX-1 is more involved in the normal functioning of organs like the stomach, while COX-2 is more involved when inflammation starts to occur. Most of the NSAIDs inhibit both COX-1 and COX-2. Recently, a few NSAIDs that selectively inhibit COX-2 have become available. These "COX-2 selective inhibitors" reduce the risks of some of the side effects associated with NSAID therapy.
