October 4, 2011 (Las Vegas, Nevada) — A lidocaine/tetracaine patch shows efficacy in relieving pain associated with shoulder impingement syndrome, according to results of a pilot trial presented here at the annual meeting of the American Academy of Pain Management.
The patch (Synera, Nuvo), already approved to provide analgesia for venous access and dermatologic procedures, has an additional feature compared with lidocaine patches in that it uses iron oxide to generate heat when exposed to oxygen, said lead author Richard Radnovich, DO, from the Injury Care Medical Center in Boise, Idaho.
"The iron oxide heats the anesthetics and drives them deeper into the tissues to get a deeper effect of numbing," he said.
Theorizing that the depth and duration of anesthesia provided by the patch (lidocaine, 70 mg, and tetracaine, 70 mg) may offer relief for the commonly tough-to-treat shoulder impingement syndrome, the researchers evaluated its efficacy in a pilot 2-week open-label study of 20 adult patients with this condition.
The patients wore 1 patch on the affected shoulder for 2 to 4 hours twice daily for 14 days, during which time no other pain medications for the shoulder pain were allowed.
Significant Pain Reduction
The results showed significant pain reduction. Compared with a mean baseline score on an 11-point Numeric Pain Rating Scale (NPRS) of 5.6 (range, 4 to 8), the scores for average and worst pain decreased by 41% ± 42% and 44% ± 7%, respectively.
Measures of pain reported by patients to interfere with general activity, normal work, and sleep decreased by 38% ± 46%, 37% ± 48%, and 43% ± 47%, respectively, with patch treatment.
Measures regarding range of motion showed improvement and mean internal rotation increased by 29° ± 21°, while mean abduction increased 41° ± 43°.
Sixty-three percent of patients showed a 2-point or greater decrease from baseline in NPRS for average pain, and 53% of patients had a 3-point or greater decrease.
Fifty-three percent of patients said they were satisfied or very satisfied with their treatment, and the patch was well-tolerated by all patients.
Side effects were described as mild or moderate erythema on the application site (50%), and 20% of patients reported mild headaches; however, no patients discontinued the treatment because of adverse events. One patient was lost to follow-up.
Shoulder impingement syndrome can be particularly frustrating for patients and clinicians alike, and even performing therapeutic exercises can be difficult because of the pain, Dr. Radnovich said. He speculated that the patch could help address the variety of challenges in treating pain related to the condition.
"The challenge is in symptom management," he explained. "Frequently patients have difficulty sleeping because lying on the shoulder can be painful, and they restrict activities because any work at or above shoulder level can hurt."
"Initially, I thought that the patch would be used to control these and other painful symptoms; for example, to reduce pain to allow the patient to sleep better or do physical therapy," he added. "Interestingly, I found that patients had a better range of motion and reduced painful symptoms even after they had stopped using the patch."
Compared with the traditional forms of shoulder impingement syndrome treatment, including nonsteroidal anti-inflammatory drugs, physical therapy, or injections, the patch provides a useful alternative.
"The Synera patch represents a possible local, noninvasive treatment that is nonsystemic and more convenient," Dr. Radnovich said.
Filling a Niche
Pain specialist William J. Granger, MD, from Marion General Hospital, in Marion, Indiana, noted that the patch does appear to potentially fill a niche for certain patients with shoulder impingement pain.
"Normally if I have a patient with impingement syndrome, I would refer them to an orthopedic surgeon for treatment, as I feel in the chronic pain arena, it is better to go ahead and treat something surgically if there is a surgical lesion present. If these patients had isolated shoulder impingement pain of a mild nature, then I could see the rationale for the Synera alternative," said Dr. Granger.
The study's findings have some tentative aspects, however, he added.
"[One question is] who really was the patient population here? Are these considered true chronic pain patients ( > 3 months) who have failed other therapies, or are they smoldering acute or subacute pain patients with shoulder impingement pain?"
In addition, the satisfaction rating from patients was good, but not necessarily great, he said.
"In terms of the results of this study, I think overall the numbers are impressive, but I would have liked to have seen a better satisfaction percentage than 53%. In the chronic pain area, however, 53% is not bad."
Dr. Radnovich was asked to consult on Nuvo's advisory board after the completion of his study. He is a speaker for Lilly, Forrest, and Covidien and has performed research for Johnson & Johnson and Pfizer. Dr. Granger has disclosed no relevant financial relationships.
American Academy of Pain Management. Presented September 22, 2011. Abstract #23.
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Cite this: Patch May Take Pinch Out of Shoulder Impingement Syndrome - Medscape - Oct 04, 2011.