Arthritis is one of the most prevalent chronic health problems and the nation's leading cause of disability among Americans over age 15. It is America's leading crippling disease. The condition affects an estimated 70 million Americans, or one in three adults. More than a million new cases are diagnosed each year. Arthritis of knee can be as disabling as any form of cardiovascular disease except stroke.
Although the cause of arthritis are not known, there are a number of contributing factors, including age, genetics (especially arthritis in hand), and obesity.
While there is no cure for arthritis, there are a number of treatments that can modify the pain and inflammation associated with it. Patients, however, may comply poorly with such treatments because of side effects or because they forgot to take a dose. Patients may turn to topical analgesics as a way to obtain relief with minimal adverse effects. Since these products are available without a prescription, they can be easily obtained. A pharmacist can help them select an appropriate topical product and teach them how to use it. But before a pharmacist can help a patient, he must first help them understand their disease. Arthritis refers to nearly 100 inflammatory conditions that affect joints and connective tissue, but the two most common forms are osteoarthritis (OA) and rheumatoid arthritis (RA).
Also known as wear-and-tear arthritis, osteoarthritis is characterized by deterioration of articular cartilage, bone hypertrophy and changes in the synovial membrane. This causes pain, stiffness, loss of movement, and inflammation. Incidence of this form of arthritis increases with age with as many as 80 percent experiencing it by age 65. According to American College of Rheumatology, more than 21 million Americans now have osteoarthritis (OA), the most common form of disease. Approximately 80% of people with OA report some form of limitation in movement activities.
Rheumatoid arthritis is a chronic inflammatory autoimmune disorder that afflicts an estimated two million Americans at a younger age and occurs more commonly in women. It appears in several joints and often in the hands and feet.
Although effective treatment is available, management of arthritis is plagued by some pervasive myths, including. The misperception that not much can be done to alleviate the pain and disability associated with the condition.
Current Drugs
Management of arthritis pain can be achieved through oral medication, non-pharmacologic approaches and external analgesics. Non-steroidal anti-inflammatory drugs (NSAIDs) are the most frequently prescribed form of therapy. While these drugs are effective analgesics in low-to-moderate doses, they are not suitable for everyone. Between two and four percent of patients taking them experience adverse reactions. Elderly people are at a higher risk as toxicity is increased with other drugs they might be taking. Research on the mechanism of pain done on a molecular level suggests that chronic inflammation from arthritis actually causes tissue changes over time. That explains why a drug that eased a person's arthritis pain for years may have gradually stopped working.
The newest generation of NSAIDS called COX-2 selective inhibitors work by blocking the work of an enzyme (cyclooxygenase 2) that sparks a cell's production of prostaglandins, the hormones that cause arthritic pain and inflammation. Compared with ibuprofen and aspirin, COX-2 inhibitors carry a low risk of causing changes in the stomach lining that can lead to ulcers. However, these category of drugs also report serious side effects that may include stomach and intestinal bleeding, heart attacks, kidney problems, liver problems and allergic reactions digestive, circulatory and cardiac problems.
Several conditions caused by the constant repetition of particular movements are referred to as repetitive strain injury (RSI). Irritation of the flexor and extensor tendons in the wrist and hands is comon injury that often affects keyborad operators and typists causing pain when fingers are moved. RSI can lead to another disorder called carpal tunnel syndrome. The carpal tunnel syndrome is characterized by numbness and pain in the thumb and middle fingers, and some tingling in the injured area. Sometimes, movement may be weakened or restricted. Some other common disorders are tennis elbow and golf elbow. Symptoms include soreness of the lateral aspect of the elbow and muscles of the forearm usually caused by excessive rotatory motions of the forearm as in playing tennis or golf.
New Drugs & Drug Research
The next generation of NSAIDS, which are being called p38 MAP kinase inhibitors, will go even further in reducing inflammatory pain. However, they are not expected on the market for several years.
Drugs that block a body chemical called tumor necrosis factor (TNF) are the major targets of research. Excess TNF plays an important role in sparking inflammation, and a class of drugs called TNF inhibitors addresses the problem in arthritic conditions such as ankylosing spondylitis and rheumatoid arthritis.
Oral Analgesics
Besides using oral NSAIDs for treatment of osteoarthritis, physicians will occasionally prescribe analgesic acetaminophen or intra-articular corticosteriods. In addition to physician prescriptions, patients may self-medicate with over-the-counter (OTC) oral analgesic products such as aspirin, ibuprofen, and naproxen to reduce both pain and inflammation. However, adverse effects are common (as with aspirin).
Therefore, there is a need for safe and effective therapy to manage pain when systemic (e.g., oral medication) therapy is not suitable or adequate. In addition to prescribed analgesic acetaminophen or intra-articular corticosteriods, patients may self-medicate with over-the-counter (OTC) oral analgesic products. However, adverse effects are common (as with aspirin).
Other Therapeutic Treatment
When systemic (e.g., oral medication) therapy is not suitable or adequate, a safe and effective therapy is needed to manage arthritis pain. Non-pharmacologic therapy, including rest, heat, cold, physical therapy and alteration of the patients' lifestyle and work activity, may also be suggested, but these measures only help to relieve pain and may only delay further joint damage.
Use of External Analgesics
Over-the-counter external analgesic products are used for a wide variety of afflictions such as aches and pains associated with musculoskeletal disorders like arthritis. They are appropriate for any patient who needs pain relief and may be used on their own or as an adjunct to systemic therapy. External analgesics may be applied to the skin to relieve musculoskeletal pain including arthritis. Adverse reactions include urticaria (hives), erythema (redness), and other cutaneous (skin) reactions. A panel of experts endorsed a number of active ingredients for use in OTC external analgesics and classifying them into four main groups, as indicated by the following representative compounds:
Menthol, a potent counterirritant produces a cooling sensation in the skin. It is a secondary alcohol extracted from peppermint and can be made synthetically. It can be found in candy, chewing gum, cigarettes and even cough drops. In concentrations from 1.25 to 16 percent, menthol possesses counterirritant properties. Counterirritant concentrations of menthol applied topically produce a feeling of coolness followed by a feeling of warmth. The sensation of cold is not due to actual cooling of the skin; menthol induces vasodilation (dilation of blood vessels), and the skin temperature at the site is actually warmer than other parts of the body. Menthol can cause sensitization in some individuals
Methyl salicylate, which occurs in wintergreen and sweet birch oil, is one of the more potent counterirritants. The recommended topical dosage is a 10 to 60 percent concentration applied three to four times daily. Methyl salicylate readily penetrates intact skin after application. Due to the possibility of percutaneous absorption, methyl salicylate should be used with caution in individuals who are sensitive to aspirin or suffer from asthma or nasal polyps. Also, patients should be told not to use heating pads in conjunction with methyl salicylate, or external analgesics in general, or to apply them after strenuous exercise, especially during hot and humid weather. These conditions can magnify the extent of systemic absorption, and in the case of methyl salicylate have resulted in reports of severe adverse reactions.
Methyl nicotinate is categorized as a vasodilator. When applied three or four times a day in concentrations of 0.25 to one percent, it is a safe and effective counterirritant. Vasodilation (dilation of blood vessels), erythema (redness) and an increase in skin temperature occur with application. Changing the concentration will not change the rate of absorption, but will increase the intensity of the reaction. The vasodilatory action of methyl nicotinate can be blocked, at least in part, by prior administration of ibuprofen or other NSAIDs, indicating the methyl nicotinate may induce vasodilation secondary to an increase in prostaglandin synthesis. When methyl nicotinate is applied over large body surface areas, generalized vasodilation can occur, and some individuals have experienced large reductions in blood pressure and syncope (fainting) as a result.
Capsaicin is the active ingredient in red chili peppers. It relieves the pain of arthritis and musculoskeletal disorders effectively, as well as pain associated with neuralgias. The same way that biting into a hot chili pepper incites a powerful stimulation of local sensory receptors in the mucous membranes, capsaicin, when applied topically in weak solutions, can cause a sensation of warmth. Adverse effects, which include burning, stinging and erythema, were localized to the site of application and normally diminished with repeated use. Other common topical ingredients include eucalyptus oil, trolamine salicylate, emu oil, MSM, witch hazel, glucosamine and chondroitin. None of these has shown significant analgesic or anesthetic efficacy when applied topically and they are not approved in the tentative final monograph for OTC external analgesics.
Safety of External Analgesics
Absorption of external analgesics through the skin is minimal when the products are used as directed, making them safe. Pharmacists play a key role in educating patients on the proper use of external analgesic products. Since external analgesics are available over the counter, patients will most likely consult a pharmacist much more commonly than their physician and statistics show that only 38 percent of Americans obtain information about arthritis from their physicians. The pharmacist, therefore, can be an invaluable resource for patients seeking arthritis relief and can help them get the most from analgesic therapy. Many arthritic patients will be taking systemic medication for analgesic and/or anti-inflammatory action. They should be advised to continue this therapy while initiating treatment of external products. Once they respond to the topical product, they may be able to decrease their dosage of systemic analgesic therapy but should do so only after consulting with their physician.
As with all medical treatments, patients should be advised to expect that a particular analgesic may reduce their pain, but rarely will any treatment, topical or otherwise, alleviate all pain associated with arthritis class.
References
- Baggaley, Ann. (2001). Human Body. Dorling Kindersley Publishing, New York, NY.
- Dox, Ida G., Melloni, J., & Eisner, G. (1993). Illustrated Medical Dictionary. Harper Collins, New York, NY.
- Enright, Elizabeth (2004). Rooting out pain. AARP - The Magazine, Sept.-Oct. pp 71-74.
- Gray, Henry. (1995). Gray's Anatomy. Barnes & Nobles Books, New York, NY.
- Gossel, Thomas A. (1994). Understanding Topical Analgesic Therapy for Arthritis Pain, U.S. Pharmacist Supplement.
- Marieb, Elaine. (1993). Human Anatomy and Physiology. The Benjamin/ Cummings Publishing Company, Redwood City, CA.
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