BOSTON — A single botulinum toxin type A injection can decrease joint pain and improve function in patients with refractory shoulder osteoarthritis, Dr. Jasvinder Singh reported at the annual meeting of the American College of Rheumatology.
In a double-blind, randomized controlled trial involving 43 patients with moderate to severe shoulder arthritis pain, 21 patients were randomized to receive a single, intraarticular injection of botulinum toxin type A (Botox) and 22 patients were injected with a placebo.
Compared with baseline, the 28-day posttherapy pain levels in the treatment group were significantly lower than those reported in the placebo group, said Dr. Singh, staff physician at the Minneapolis VA Medical Center.
In particular, 38% of the patients who received the botulinum injection achieved a minimum 30% improvement in pain scores, compared with a 9% improvement among patients in the placebo group.
Preliminary animal and clincial studies have shown that neurotoxin injection for sustained analgesia is a promising approach to persistent joint pain, said Dr. Singh, noting that the agent may decrease pain by inhibiting vesicle release of neuropeptides—including substance P and calcitonin gene-related peptide—and by disrupting nociceptor function.
The current study assessed the efficacy of the neurotoxin in patients with chronic arthritis-associated shoulder pain who had failed to respond to corticosteroids or other pain medication and who were not candidates for shoulder arthroplasty.
All of the patients had a 6-month history of moderate to severe shoulder pain, which is categorized as greater than 4.5 (on a scale ranging from 0 to 10).
Patients randomized to the treatment intervention received a single injection of 100 units of botulinum toxin type A plus lidocaine, and patients in the placebo group received a single injection of saline plus lidocaine.
Patients were assessed using the Visual Analog Scale (VAS), a numeric rating scale (NRS) for day pain, and the Shoulder Pain and Disability Index (SPADI) pain subscale, said Dr. Singh.
Secondary outcomes included SPADI scores and the proportion of patients achieving clinically meaningful pain relief, defined as a minimum 30% improvement. At baseline, pain outcome variables between the intervention and placebo groups were comparable.
At day 28, the mean VAS pain score in the treatment group was 4.12, significantly lower than the mean 6.54 in the placebo group. Day pain, according to NRS and SPADI pain scores, was significantly improved in the treatment group.
The SPADI score was better at day 28 in the treatment group compared with that in the placebo group, with a trend toward significance, Dr. Singh said.
The investigators are analyzing the duration of the analgesic effect and the associated adverse effects.
The findings thus far provide “the initial proof of concept of effectiveness of botulinum toxin injection for relief of shoulder pain,” Dr. Singh said, adding they need to be replicated in a larger, multicenter, randomized trial before the treatment can be recommended.
Dr. Singh reported having received travel funds for previous research projects from Allergan Pharmaceuticals, maker of Botox. The current study was funded by the Arthritis Foundation, the Mayo Clinic, and the Minneapolis VA Medical Center.