PALM SPRINGS, CALIF. — Patients with low back pain who experience significant improvement in pain and function after one set of botulinum toxin type A injections are highly likely to respond to subsequent treatments, Bahman Jabbari, M.D., reported at the annual meeting of the American Academy of Pain Medicine.
Those who do not obtain relief within about 2 weeks of an initial series of injections are significantly less likely to respond to subsequent treatments, said Dr. Jabbari, professor of neurology at Yale University, New Haven.
A prospective study of 75 adults with chronic, refractory low back pain was undertaken by Dr. Jabbari and his associates at Walter Reed Army Medical Center, Washington.
Botulinum toxin type A (Botox, 100 U/cc) was injected into paraspinal muscles at three to five horizontal levels (50 U/site) on each side as close as possible to the tender points, said Dr. Jabbari, who presented the data in poster form. The mean dose per session was 285 U, with a range of 200–450 U, depending on the patient extension and laterality.
Patients received neurologic examinations and were administered a visual analog pain assessment, Oswestry Low Back Pain Questionnaire, and the Pain Impact Questionnaire at baseline, 3 weeks, and 2, 4, 6, 8, 10, 12, and 14 months after the initial treatment. They could request subsequent Botox injections when pain recurred, usually at 4, 8, and 12 months. Pain medications and physical therapy were not adjusted during the study.
Significant pain relief and improvement in function were noted by 42 of 75 patients at 3 weeks and 40 of 75 patients at 2 months. Of these patients, 90% continued to respond to subsequent treatments. Those who did not obtain initial relief were unlikely to respond during future treatments.
No serious adverse events were reported. Two patients experienced a transient flu-like reaction, and another described acute root pain for 60 seconds after being injected.
Age, pain intensity, pain duration, laterality, and a history of previous surgery all failed to correlate with whether a patient responded or failed to improve with Botox.
He noted that patients who respond generally begin to notice improvement within 3–4 days of an initial injection session. Relief typically peaks at about 10 days to 2 weeks and generally lasts about 4 months.
Allergan Inc. provided funding for the study.