Ingredient of Viagra may help to avoid wheelchair

A Canadian study involving mice shows that anti-impotence pills might protect the hearts of people with a common form of muscular dystrophy.

Canadian researchers gave sildenafil, the active ingredient in drug maker Pfizer Inc's Viagra, to mice with an animal version of Duchenne muscular dystrophy, and found that it improved their heart performance.

They said it would be premature to give Viagra to people with the disease, but said the results indicate the drug potentially could be used to prevent or delay heart failure in children with Duchenne muscular dystrophy.

The mice were given doses of the drug comparable to those administered to treat erectile dysfunction in men. The study, published in the Proceedings of the National Academy of Sciences, showed that sildenafil cut the levels of damage to contracting heart muscle cells.

"If you don't give the sildenafil, the heart of these mice doesn't function as well as normal mice, and they are more susceptible to stress-induced cell death," said researcher Christine Des Rosiers of the Montreal Heart Institute.

She said in an interview the drug worked to improve heart performance in the mice by preventing the breakdown of a naturally occurring chemical. Called cyclic guanosine monophosphate, or CGMP, it is involved in a number of cellular signaling pathways.

Duchenne muscular dystrophy is an inherited wasting disease characterized by weakness and progressive degeneration of the muscles, including the heart muscle. It begins in the legs and pelvis, and later affects the whole body. Most people with the disease must use a wheelchair by about age 12. It is caused by a genetic mutation of dystrophin, a protein vital to muscle cells.

Heart problems can appear at around age 10 and they progress quickly, affecting most people with the disease by age 20. These heart problems are an important cause of death among patients with muscular dystrophy.

Sildenafil was developed as a heart drug and is widely prescribed for erectile dysfunction as well as pulmonary hypertension. The researchers said discussions are under way about possible future studies using the drug in patients with muscular dystrophy.