BOTULINUM TOXIN TYPE B (MYOBLOC™) IN THE TREATMENT OF REFRACTORY MYOFASCIAL PAIN

Dorene Taqi, Ian Gunyea, PA‐C, Bhadresh Bhakta, MD, Venkatesh Movva, MD, Sameh Ward, MD, Mike Jenson, PA‐C, CPP, Mike Royal, MD Pain Evaluation and Treatment Center, 5801 East 41 st Street, Suite 1000, Tulsa, OK 74135 (918) 622‐3888; fax: (918) 828‐9050; email: royal@tulsapain.com Myofascial pain syndrome (MPS) is a common chronic pain syndrome defined by the presence of trigger points and referred pain (Travell, Simons, 1983). Myobloc™ (Botulinum toxin type B [BTB], Elan Pharmaceuticals) was FDA‐approved last year for the treatment of cervical dystonia. A retrospective review of 32 patients who received BTB for treatment of refractory MPS was performed. These data were added to an additional 8 patients who received BTB in a prospective fashion as part of a phase I study evaluating BTB in lower back myofascial pain. Forty patients (32 retrospective, 8 prospective; 25F: ages 34–78y/15M: ages 35–81y) received BTB injections into affected muscles, e.g., cervical/thoracic (22), lumbar (12), and piriformis (6). The injections were performed as standard trigger point injections by palpation using Myobloc™ 500–2500 units/site in 0.5–2 ml (0.5% bupivacaine was used to dilute to the desired concentration). Patients received up to 18,000 units total dose. Patient global response rates, McGill short form pain questionnaire, VAS scores and side effects were monitored. No significant side effects were noted. Response to injection was defined as poor (=30% symptom reduction), fair (30–49% reduction), good (50–69% reduction), and excellent (=70% reduction). Twenty‐three patients reported good (12/40) to excellent (11/40) pain relief lasting an average of 3.3 months. An additional 8 patients reported fair responses. During the response phase, the patients who responded well to Myobloc™ were able to tolerate a more aggressive therapeutic exercise program. Controlled prospective trials of BTB in myofascial pain would be desirable. Travell JG, Simons DG. Myofascial pain and dysfunction: the trigger point manual. Vol. I. Baltimore, MD: Williams & Wilkins;1983. The prospective study was supported by a research grant from Elan.