Nov. 9 (HealthDay News) -- Botox seems to relieve shoulder pain in arthritis sufferers, a preliminary study found.

"We don't recommend people start using it until we have the definitive study," said study author Dr. Jasvinder Singh, a staff physician at the Minneapolis VA Medical Center. He said his study was small, and more patients needed to be assessed before the treatment could be recommended.

Singh was to present his findings Friday at the American College of Rheumatology annual meeting, in Boston.

Singh and his colleagues randomly assigned 43 patients with moderate-to-severe osteoarthritis pain in their shoulders to one of two groups. One group received a single dose of the botulinum toxin type A and lidocaine, a local anesthetic. The other group got a dose of saline (salt water) plus the lidocaine. Neither group knew what they were receiving.

Osteoarthritis is the "wear-and-tear" type of arthritis, and the risk for it increases with age, obesity and other factors. About 21 million Americans have this form of arthritis, according to estimates from the Arthritis Foundation.

More than 5 percent of adult Americans suffer shoulder pain lasting more than a month in a given year, according to Singh. At the start of the study, the participants' pain levels were greater than 4.5 on a scale of zero to 10, with 10 being the worst pain.

The researchers compared the pain levels before the botulinum treatment to levels assessed 28 days later. They found that 38 percent of the botulinum group had a 30 percent or better reduction in their pain scores, compared to 9 percent of the saline group. Those who got botulinum also reported more improvement in shoulder function than the saline group.

The toxin may work, Singh speculated, by reducing the release of certain proteins from nerves in the joint. And that, in turn, may decrease the pain sensation.

Dr. John Hardin is chief science officer at the Arthritis Foundation, and a professor of medicine at Albert Einstein College of Medicine, in New York City. He agreed that more study of botulinum for arthritis pain was needed but was optimistic. "It appears very promising, that this is useful in achieving pain relief," he said.

Hardin added a caveat, however: "It probably needs to be made clear this is not thought of as an intervention that stops the progression of the disease." And he warned those who might get the treatment that just because the pain was reduced didn't mean the disease had gone away.

"It's still in the experimental stage," Hardin said.

Besides easing facial wrinkles, Botox is also used to treat bladder problems, migraine headaches and excess sweating, among other conditions.

The new study was funded by the North Central chapter of the Arthritis Foundation, the Mayo Clinic Center for Clinical and Translational Research, and the Minneapolis VA Medical Center. In the past, Singh has received travel funds for other research projects from Allergen Pharmaceuticals, which makes Botox, he said.

SOURCES: Jasvinder A. Singh, M.B.B.S., M.P.H, staff physician, Minneapolis VA Medical Center, and assistant professor of medicine, University of Minnesota School of Medicine, visiting scientist and K-12 scholar, Mayo Clinic School of Medicine; John Hardin, M.D., chief science officer, Arthritis Foundation, Atlanta, and professor of medicine, Albert Einstein College of Medicine, New York City; Nov. 9, 2007, presentation, American College of Rheumatology annual meeting, Boston