APS: Botulinum Toxin Type B Promising for Treatment of Refractory Myofascial Pain

By Jill Stein, Special to DG News

BALTIMORE, MD — March 18, 2002 — Nearly two-thirds of patients obtain at least a 50 percent reduction in symptoms of refractory myofascial pain syndrome (MPS) after treatment with Botulinum toxin type B (BTB), new findings suggest.

The data were presented at the 21st Annual Scientific Meeting of the American Pain Society (APS) by Dr. Dorene Taqi, from the University of Oklahoma College of Medicine in Tulsa, Oklahoma, United States.

Her group retrospectively reviewed 32 patients who had received BTB for the treatment of refractory MPS. These data were added to an additional eight patients who received BTB in a prospective manner as part of a phase I study evaluating BTB in lower back myofascial pain.

The forty patients received BTB injections into affected muscles. The injections were performed as standard trigger point injections by palpation using BTB 500 to 2500 units/site in 0.5-2 ml (0.5% bupivicaine was used to dilute to the desired concentration).

The response to injection was defined as poor (referring to a 30 percent symptom reduction), fair (referring to a 30 to 49 percent symptom reduction), good (referring to a 50 to 69 percent symptom reduction), and excellent (referring to a 70 percent reduction.

Twelve patients reported good and 11 patients reported excellent pain relief lasting an average of 3.3 months. An additional eight patients reported fair responses.

During the response phase, the patients who responded well to BTB were able to tolerate a more aggressive therapeutic regimen. No significant side effects were observed.

Dr. Taqi said that the results show that nearly 60 percent of MPS patients who are treated with BTB have at least a 50 percent decrease in symptoms. Botulinum toxin type B, she added, may reduce the symptoms of and disability associated with MPS by breaking the pain/spasm cycle, giving the patient a "window of opportunity" for conservative measures to have a positive impact.

She also noted that lower doses (2500 to 5000 units) appear to produce a definite, but shorter-lived response (four to eight weeks). Increasing the dose appears to produce response rates exceeding three months.

Finally, the major benefit of BTB is that the duration of response is several months compared with trigger point injections which typically last only days to weeks.

The prospective portion of this study was supported by a research grant from Elan Pharmaceuticals.

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