by Nathan Wei, MD, FACP, FACR
Nathan Wei is a nationally known board-certified rheumatologist and author of the Second Opinion Arthritis Treatment Kit. It's available exclusively at this website... not available in stores.
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Botulinum toxin or “botox” is being scrutinized more carefully as a possible treatment for certain arthritis conditions.
Intra-articular injections of botulinum A toxin (Botox, Allergan) decrease refractory joint pain and improve function, according to the first-ever study looking at the use of this toxin in joints. The new findings were reported at the American College of Rheumatology 2004 meeting.
In this open-label, pilot study, 7 frail elderly patients with shoulder pain received intra-articular injections of 50 to 100 units of Botox into the joint and 5 patients with refractory lower-joint pain received intra-articular injections of 25 to 50 units of the toxin.
"There was a striking decrease in pain within 4 to 6 weeks after injection, and several people's pain continued decreasing until after 2 months. Thereafter, there was a gradual increase in pain," says Dr Marin L Mahowald (University of Minnesota Medical School, Minneapolis)."This may be an interim treatment to delay surgery."
Overall, pain relief lasted 3 to 12 months, according the 1-year follow-up data. Three patients had a slow increase in pain, but not to the pre-injection levels of severity.
Among shoulder-pain patients, there was a 71% mean maximum decrease in shoulder pain 4 to 12 weeks after injection, dropping from 8.2 to 2.4 on a 0-10 score of ascending pain severity. In addition, this group showed a 67% increase in degree of forward flexion and a 42% increase in degree of active abduction. Patients who had injections in their lower-extremity joints had a 55% mean maximum decrease in joint pain and severity 4 to 12 weeks after injection. This group also achieved a 36% improvement in the time to perform sit-to-stand exercises 10 times, down from 36 seconds before to 23 seconds after the injection.
Mahowald injected a total of 15 joints (9 shoulders, 3 knees, and 3 ankles). There were 9 male and 2 female patients, with an age range of 42 to 82, including 5 rheumatoid arthritis (RA) patients, 1 psoriatic arthritis patient, and 5 osteoarthritis (OA) patients. In the study, 14 of 15 joints injected achieved a 30% reduction in pain and 10 of 15 joints had a 50% or greater pain reduction. Patients requested reinjection of 2 shoulders at 3 months, 2 shoulders at 9 months, and a knee at 10 months. Botox was effective on reinjection. Since completing this study, Mahowald says that she has even done 1 injection into a hip joint, and "it worked."
Exactly how this toxin works to reduce joint pain is not known, but Mahowald suspects it inhibits the release of neuropeptides involved in pain production and transmission. She initiated the trial without any pharmaceutical support based on preliminary data in animals showing it may have an effect, positive reports of its use in cervical dystonia, and its serendipity as a migraine treatment.
Safety "was a big concern," she says, especially given its off-label use and the unique mode of injection used in this study. However, there was no increase in joint swelling, erythema, tenderness, fatigue, or dyspnea. In addition, no adverse events were seen among patients who were reinjected.
"These encouraging results must be verified by randomized placebo-controlled trials, which are under way," Mahowald cautions. The new study involves injecting of 100 units of Botox or saline into shoulders and knees.
The primary outcome is pain at 1 month. If there is no reported pain relief, subjects can roll over into an open-label trial. The new trial will also assess function with the Western Ontario and McMaster University Osteoarthritis Index (WOMAC), and SF-36 will be used to measure quality of life. Currently, Botox is US FDA-approved to treat strabismus, blepharospasm, hemifacial muscle spasm, glabellar lines, and severe primary axillary hyperhidrosis.
Botox has been used by other investigators for both low back and neck disorders. It is injected directly into the muscle and appears to work by eliminating the severe muscle spasm which affects many patients who have osteoarthritis in both the neck and low back.
Single treatment with botulinum toxin A gives several months' relief of low back pain.
More usually encountered as the culprit of severe food poisoning, the commercially available version of botulinum toxin A, Allergan's Botox®, has found a number of medical uses in recent years, as well as hitting headlines with its unlicensed cosmetic uses. The product is approved for use in cervical dystonia (and also cerebral palsy in Europe), and has been reported to be of benefit in essential hand tremor, upper limb spasticity after a stroke, and certain types of migraine/headache. (The localized paralysis that it produces, by its action of blocking the neuromuscular junction, has also been exploited by the cosmetic surgery industry for the relief of "brow furrow lines").
The latest medical use to be reported is the relief of chronic low back pain, as outlined in a small clinical study published in the May 22nd issue of Neurology . Lead author Dr Bahman Jabbari, neurologist at the Walter Reed Army Medical Center, Washington DC, says further studies are needed because of the small numbers involved. However, as this is the first double-blind study to show efficacy of botulinum toxin A in chronic low back pain.
The study involved 31 patients who had suffered chronic low back pain for an average of 6 years (minimum duration =6 months) and were being treated with a variety of analgesic and antispasmodic drugs, antidepressants, and muscle relaxants. They were treated in a randomized double-blind fashion with injections of saline or botulinum toxin A (200 U administered as 40 U at five different lumbar paravertebral levels on the sites of maximum discomfort) and advised to continue with previous medications at the same doses.
Significantly more patients treated with the toxin than with placebo reported that their pain had diminished by 50% or more at both 3 week and 8 weeks after the injection and reported an improvement in their ability to function at 8 weeks. Pain and degree of disability were documented on the Visual Analog Scale (VAS), and the ability to function on the Oswestry Low Back Pain Questionanire (OLBPQ), which includes questions about everyday activities such as walking, lifting, and traveling.
No patients reported side effects from the injections, and no patient treated with botulinum toxin reported worsening of pain or function after the injection, although 2 patients on saline did so. Of the 15 patients treated with the toxin, 6 were re-evaluated at 6 months. They reported that the drug's effects had worn off after 3-4 months.
Exactly how the benefit is achieved is unclear. Botulinum toxin is known to reduce the amount and severity of muscle spasms. Jabbari speculates that it may also reduce pain by decreasing input from sensory fibers or by acting on pain receptors. He says further studies are needed to investigate whether repeated injections continue to help ease the pain. "That has been the case for patients who receive botulinum toxin for other disorders, such as dystonia and spasticity, so hopefully that will be true for people with low back pain as well," he points out.
Foster L, Clapp L, Erickson M, Jabbari B. Botulinum toxin A and chronic low back pain: a randomized, double-blind study. Neurology 2001 May 22; 56(10):1290-3.
Currently, botulinum toxin is being evaluated at the Arthritis Treatment Center in Frederick, Maryland where it is being used for patients who have refractory pain accompanied by muscle spasm related to severe osteoarthritis affecting the neck and low back. It has also been used successfully to treat plantar fasciitis at ATC.
It must be cautioned that botox is not yet approved by the FDA for this indication. Further study is still required.
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