The role of substance P in rheumatic disease

Therapeutic effects of intra-articular botulinum neurotoxin in advanced knee osteoarthritis

BACKGROUND

Osteoarthritis (OA) is a major cause of musculoskeletal pain that causes morbidity, physical limitation, and poor quality of life. The purpose of this study was to evaluate the therapeutic effects of intra-articular (IA) injection of botulinum neurotoxin A (BoNT/A) for advanced knee OA.

METHODS

Twenty-four patients (38 knees) were enrolled, and the subjects were radiographically verified as having stage III or IV OA according to the Kellgren-Lawrence classification. We used the Western Ontario and McMaster Universities Osteoarthritis Index to evaluate the therapeutic effects monthly for 6 months. BoNT/A (100 U) was reconstituted with 4.0 mL saline and was injected into the symptomatic knee joints after baseline evaluation and 3 months later.

RESULTS

The therapeutic effects of BoNT/A were clinically significant at 1 month after the first injection, but statistical significance was not noted until 3 months after the first IA injection. Pain and stiffness improved clinically; however, the effect of BoNT/A achieved statistical significance only for the pain subscale in stage III OA. There was no significant difference between the stage III and IV groups. There was no significant muscle atrophy or serious adverse effect in any group after treatment.

CONCLUSION

IA BoNT/A provides a new therapeutic option for refractory pain in patients with advanced knee OA. Although IA BoNT/A appears to be effective and safe for the management of advanced knee OA, these results cannot be generalized to patients with mild knee joint pain or nonspecific soft tissue pain in the knee joint region.

Intra-articular Botulinum Toxin Type A: a new approach to treat arthritis joint pain

There is a growing need for novel treatments of refractory arthritis joint pain as the aging population is expanding with many patients who are unable to undergo joint replacement surgery. We are studying the efficacy and safety of intra-articular injection of Botulinum Toxin Type A (IA-BoNT/A) into joints with arthritis pain. In several small open label studies, initial effects for IA-BoNT/A were encouraging because two thirds of the patients had more than 50% reduction in joint pain severity that was associated with a significant improvement in function. Importantly no serious adverse effects of IA-BoN/A were noted. Based on these initial results, we have completed two pilot randomized controlled trials in painful shoulder joints and painful knee joints. In the shoulder study, IA-BoNT/A produced a significant decrease in shoulder pain severity at one month (6.8-4.4 on VAS, p=.002) that was also significantly better than the non-significant change after IA-Saline placebo (1.6 unit difference favoring IA-BoNT/A, p=.014). In the knee study IA-BoNT/A produced a significant 48% decrease in McGill Total Pain Score at one month (p=.01 1) that was still significant at 3 mo after injection (p=.002). There was a strong placebo response in one third of those but the decrease in pain severity was not significant. We are currently conducting a RCT of IA-BoNT/A for painful prosthetic knee joints. Based on these initial studies of IA-BoNT/A we have gone 'back to the bench' to standardize a menu of pain behaviors for mice with acute inflammatory arthritis pain and chronic inflammatory arthritis pain. IA-BoNT/A significantly reduced arthritis joint tenderness (evoked pain score) in acute and chronic inflammatory arthritis and normalized impaired spontaneous wheel running in mice with chronic inflammatory arthritis but not in those with acute inflammatory arthritis. With these models of arthritis and pain behavior methods we will be able to screen potential intra-articular analgesics, define dose response curves and injection schedule, and study the relationships of articular pain and loss of function.

Topical agents in the treatment of rheumatic disorders

Topical drug delivery may be the optimal route for the treatment of localized musculoskeletal disorders because higher drug concentrations can be achieved at the sites of clinical significance. The rationale for the use of topical salicylates and other nonsteroidal anti-inflammatory drugs (NSAIDs) in the treatment of soft-tissue rheumatic complaints and osteoarthritis is reviewed. Topical capsaicin offers another potentially beneficial therapy for the treatment of osteoarthritis of selected joints. Although there are extensive, uncontrolled experiences with DMSO that suggests its effectiveness in the treatment of musculoskeletal disorders, controlled trials yield conflicting results. The basis for the use of physical modalities such as phonophoresis and iontophoresis to improve topical drug efficacy is summarized.

Non-NSAID pharmacologic treatment options for the management of chronic pain

Chronic pain affects 75 million US citizens. A number of pharmacologic treatments are available for chronic pain that does not respond adequately to nonpharmacologic methods. Long the mainstay of chronic pain management, nonsteroidal anti-inflammatory drugs (NSAIDs) are known to be associated with gastrointestinal (GI) and renal toxicities, a particular problem for the elderly population, which commonly experiences chronic pain, such as that associated with osteoarthritis (OA). Several non-NSAID, non-narcotic therapies are available for noninflammatory pain. Acetaminophen is as effective as NSAIDs for the management of mild-to-moderate OA pain and is the recommended first-line therapy by the American College of Rheumatology (ACR). Propoxyphene, widely believed to be safe and effective, may, in fact, be no more effective-and perhaps less effective-than acetaminophen or ibuprofen. A relatively new analgesic, tramadol, appears to be a useful therapy for patients who do not receive adequate pain relief with acetaminophen and are at risk for NSAID-related side effects. For localized chronic pain associated with OA, topical capsaicin is also an effective analgesic.

Chronic pain states: pathophysiology and medical therapy

OBJECTIVE

The pathophysiology and management of chronic pain are reviewed in this two-part article, with an emphasis on pharmacological therapies and surgical interventions.

DATA SOURCES

A thorough literature review of published articles available in Medline from 1966 to 1996 on the topic of pain management, including diagnosis, pathophysiology, interventions, and treatment.

CONCLUSIONS

Despite the development of new instruments and treatments to assess and manage pain, chronic pain is often poorly understood and inadequately addressed. Caregivers often lack sufficient skills to intervene promptly and effectively. Traditionally, drug therapy has relied on the nonsteroidal antiinflammatory drugs (NSAIDs) and opioid analgesics for chronic nociceptive pain. A newer analgesic choice for moderate to moderately severe pain is tramadol, a centrally acting agent with at least two complementary mechanisms of action and minimal gastrointestinal or renal toxicity. Adjuvant agents, including tricyclic antidepressants (TCAs), anticonvulsants, and local anesthetics, also help manage chronic neuropathic pain. Although significant advances in the understanding of chronic pain and its pathophysiological mechanisms and newer techniques (noninvasive and invasive) for chronic pain management have become available, reduced patient morbidity and improved quality of life may only be realized with an improved understanding of available resources.

Approach to the management of nonmalignant pain

Pain is a universal, subjective, unpleasant sensation. It results from a noxious stimulus that causes the body to perceive existing or potential damage to its organs. The biochemical mechanism of pain is based on peripheral nociceptors that preferentially receive noxious stimuli and thereafter cause the primary afferent nociceptor fibers to release endogenous chemicals such as bradykinin, histamine, prostaglandins, serotonin, norepinephrine, and substance P. Additionally, substance P may stimulate prostaglandin and collagenase production, thus providing an explanation for the effectiveness of anti-inflammatory drugs in relieving pain. The interpretation of pain is highly individualized and embodies the entire personality. Thus, no two patients with pain can be treated in the same way. Pain is assessed through medical history, physical examination, and a variety of pain scales. General principles in managing pain call for the physician to (1) respect pain; (2) recognize the psychologic components of pain; and (3) treat the underlying disorder in a timely fashion. Modern management of pain evokes a multidisciplinary approach that includes patient education, pharmacologic intervention, physical medicine, minimally invasive procedures, psychologic counseling, behavioral modification and, in some instances, surgery or a variety of other nonpharmacologic modalities.