TUESDAY, Feb. 22 (HealthDay News) -- Nitroglycerin ointment, usually prescribed to relieve chest pain, may also counter bone loss, a new study suggests.

As the population ages, the number of women with osteoporosis is increasing. Nitroglycerin appears to increase bone density and prevent bone loss, and it may have advantages over newer and more costly drugs, the researchers noted.

"Nitrates are widely available and inexpensive," said lead researcher Dr. Sophie A. Jamal, an assistant professor of medicine at Women's College Research Institute and University of Toronto. "Our study demonstrates that nitrates are able to increase bone size and strength, which may reduce the incidence of fractures worldwide."

However, whether or not this treatment actually reduces fractures is unknown. "These are promising early findings. Further, larger studies need to be done to confirm our findings and to determine if nitrates can reduce fractures," Jamal said.

The treatment seems to work by producing nitric oxide, which may aid in stimulating bone growth, the researchers noted. The report is published in the Feb. 23 issue of the Journal of the American Medical Association.

For the study, Jamal's team randomly assigned 243 postmenopausal women to nightly doses of nitroglycerin ointment or placebo. The ointment was spread on a one-inch strip on the upper arm.

To test the effectiveness of the treatment, the researchers measured bone density at the spine, thigh and hip. The trial ran for two years.

Compared with women receiving a placebo, women who received nitroglycerin ointment had a 6.7 percent increase in bone density in the spine, a 6.2 percent increase in the hip and a 7 percent increase at the top of the thigh bone, the researchers found.

The most common side effect of the nitroglycerin ointment was headache. Among those receiving the ointment, 35 percent reported headaches, compared with 5.4 percent among women receiving placebo, the report indicated.

Dr. Sundeep Khosla, a professor of medicine at the Mayo Clinic and author of an accompanying journal editorial, said that "while there are a number of drugs available to prevent or treat osteoporosis, most work to prevent further breakdown of bone, rather than build new bone."

However, nitroglycerin can actually stimulate the formation of new bone, he added. "Here's a drug that's been in use for decades to treat chest pain due to angina, that prevents bone loss and increases bone mass," he said.

Khosla thinks these findings are promising, but a large-scale study looking at whether the treatment prevents fractures is needed before nitroglycerin ointment can be recommended as a standard treatment.

"There are a lot of steps between what this study has shown before patients should ask for it or doctors should prescribe it specifically for osteoporosis," he said.

The study was funded by the Canadian Institute of Health Research and the Physicians' Services Incorporated.

Nitroglycerin ointment is fairly inexpensive and depends on how much one buys. For example, 30 grams of nitroglycerin ointment costs about $30 and that's good for about 2,000 applications at the dose used in the study.

Another report in the same journal found that older women taking drugs called bisphosphonates, such as Fosamax or Boniva, to prevent bone loss were at risk for rare fractures of their thigh bone.

This finding has been shown before and caused the U.S. Food and Drug Administration to start monitoring these rare fractures.

The risk appeared highest among women taking the drugs for five years or more. However, the absolute risk is very small and these drugs do prevent more common types of fractures, according to study author Dr. Laura Y. Park-Wyllie, of the Li Ka Shing Knowledge Institute of St. Michael's Hospital in Toronto.

"These findings also highlight the need for a thoughtful assessment of individual risk of fracture when considering extended bisphosphonate therapy, and that long-term use of these drugs may warrant reconsideration, especially in patients at relatively low risk of fracture. It may be appropriate to consider a drug holiday for selected patients, particularly as the cumulative duration of bisphosphonate therapy surpasses five years," Park-Wyllie and colleagues wrote.

However, they added that their study "confirms the known benefits of bisphosphonate treatment for typical osteoporotic fracture, and evidence suggests that bisphosphonate therapies are underused in individuals at high risk of fracture despite their established efficacy."

More information

For more information on osteoporosis, visit the U.S. National Library of Medicine.