Heated lidocaine/tetracaine patches may treat shoulder impingement syndrome

By Rob Goodier

NEW YORK (Reuters Health) - Daily applications of heated lidocaine/tetracaine patches may treat shoulder impingement syndrome about as well as a corticosteroid injection, according to a new study presented September 5th at the Pain Week conference in Las Vegas.

"Physicians may want to consider using the patch as an alternative to physical therapy or injections for patients with shoulder impingement syndrome or typical rotator cuff problems," although it is too soon to make firm recommendations, Dr. Richard Radnovich at Injury Care Medical Center in Boise, Idaho, who led the study, told Reuters Health by email.

"This could apply to patients who are opposed to using steroids, who do not tolerate injections or cannot afford the time or expense of physical therapy. Another potential use is by physicians who do not perform injections," Dr. Radnovich says.

Shoulder impingement syndrome is a common cause of shoulder pain characterized by the impingement of tendons of the shoulder. Steroid injections are often used if conservative treatment with rest, ice packs, oral anti-inflammatories and physical therapy fails.

In a six-week open-label study, the researchers randomized 60 people to treatment with up to two patches daily for two weeks or a single steroid injection. Those who used the patches could continue the treatment as needed for two more weeks.

At the start of the study the patients in both groups rated their shoulder pain at an average of 5.6 to 6 on a scale of 0 to 10. Two weeks later, all of the patients reported statistically significant improvement with no statistical differences between the groups.

Those using the patch had a 35% decrease in pain, compared to a 42% decrease in those who received an injection. The improvement lasted through the end of the study at the sixth week, when both groups of patients reported a 43% pain reduction.

Both groups also had significant improvements in range of motion after two weeks that lasted through the end of the study. According to the study protocol, treatment failed for two patients in the patch group and six in the steroid group because they had to take acetaminophen for two days in a row to control their pain.

The patch, marketed now as the Synera Patch, is approved for use in the United States for dermatological procedures but not for impingement pain.

"Nuvo Research is currently in communication with FDA discussing the regulatory path for obtaining a new indication for acute musculoskeletal pain. By the time the program is run and the FDA reviews it, this is probably three years away," says Arnold Gammaitoni, who was involved in this study as Vice President of Scientific Affairs at Nuvo Research in West Chester, Pennsylvania.

Some questions about the patch remain. While the study suggests that this noninvasive approach might have a short-term effect, it would be interesting to see the results after three to six months, says Dr. Alfred Mansour, an orthopedic surgeon at the University of Texas, Houston, who was not involved in the study.

"An unanswered question is how a topical anesthetic can have similar results to a locally-delivered anti-inflammatory medication (corticosteroid). (They) should have different modes of action and (it) would be interesting to see if their combined use had an added effect," Dr. Mansour told Reuters Health.

Dr. Radnovich has used the patches with his patients and he was surprised to see longer-term improvement, he says.

"This finding reinforces the premise that our current models for understanding tendonopathies is limited. And our current treatments may need to be reevaluated," Dr. Radnovich said.