Viagra May Help Muscular Dystrophy Patients

Oct. 19, 2010— -- Though young boys may seem like unlikely candidates for treatment with Viagra, new research in mice suggests that the drug -- usually prescribed for erectile dysfunction -- may one day be used to minimize heart problems for pre-teen and adolescent boys with Duchenne muscular dystrophy.

Since Viagra (sildenafil) was approved for erectile dysfunction in 1998, researchers have identified a number of other conditions that benefit from the famed "little blue pill," such as pulmonary hypertension, heart problems in severely premature infants, and decreased circulation in patients with gangrene. New research suggests it might even help treat prostate cancer.

Now Viagra has the potential to become a heart helper for young boys who are just beginning to suffer from cardiac degeneration due to Duchenne muscular dystrophy (DMD).

Duchenne muscular dystrophy is a degenerative, muscle-wasting disease that usually affects young boys, though girls can be carriers of the disease. It causes progressive muscle weakness and loss, usually confining patients to a wheelchair by around age ten. It often leads to death before age 30. In later stages, degeneration of the diaphragm and heart can lead to potentially fatal breathing complications and heart failure.

With the help of better treatments for and control of these respiratory problems, many patients are now living into their late twenties and thirties -- long enough to suffer from cardiac complications seen in very late stages of the disease, says Stanley Froehner, a professor of physiology and biophysics at the University of Washington, Seattle, and a co-author on the study.

"It's a disease of skeletal muscular degeneration, but there's also a significant impact on the heart. Some of the boys [with DMD] in the past have died of cardiac failure, but it's becoming more common now that patients are living longer," Froehner says.

Using mice bred to mimic DMD, researchers found that treatment with Viagra was able to normalize abnormal heart function in these mice within a few days. When given to mice that had not yet shown cardiac symptoms, the drug also appeared to delay the onset of cardiac symptoms.

Heart Help for Little Boys With Muscular Dystrophy

Duchenne muscular dystrophy is the most common type of the disease and is caused by a problem with the gene that makes a protein called dystrophin. It affects an estimated one in 3,500 males, according to the National Institutes of Health.

Current treatments include physical therapy to preserve mobility, drugs to manage the muscle weakness and spasm and corticosteroids to reduce inflammation and possibly delay the progress of the disease. If patients live long enough to be faced with cardiac complications due to the breakdown of the heart tissue, cardiologists can prescribe blood pressure medication to lessen the strain on the heart, says Christopher Rosa, board member for the Muscular Dystrophy Association.

Rosa himself suffers from Becker muscular dystrophy and is currently taking blood pressure medication to treat the beginnings of cardiomyopath, or weakening of the heart.

Past research has shown improvement in heart performance with drugs, such as Viagra, that prevent the breakdown of a compound called cGMP. As Viagra's safety profile has already been vetted by the FDA, it is an attractive candidate for potential treatment, Rosa notes.

The exact mechanism through which increasing cGMP helps cardiac complications in Duchenne muscular dystrophy patients is not clear, but research is suggestive enough to have spurred a few clinical trials testing Viagra in these patients, says Joseph Beavo, a professor of pharmacology at the University of Washington and a co-author on the study.

Viagra as Double-Duty Drug

Clinical trials are in process to test Viagra in older boys with DMD, but Froehner says his team hopes to test this treatment on younger boys aged 8 to 12 who do not yet show clinically significant heart problems. He says the dosage would most likely be above what is normally given to treat erectile dysfunction.

If clinical trials go well, cardiomyopathy due to Duchenne muscular dystrophy could become yet another off-label use for drug-maker Pfizer's popular ED drug. Though Viagra is already FDA approved, under the name Ravatio, to treat pulmonary hypertension, the drug has been used off-label by doctors for various problems related to circulation and heart function.

Some physicians have use the drug to treat infants with breathing problems with great success, Dr. Jerril Green, a critical care specialist at the Arkansas Children's Hospital in Little Rock, told ABCnews.com. In 2003, Green treated a boy named Chance Collins, then two years old, who was born three months prematurely and suffered from severe lung problems.

"The Viagra opens up the arteries in these children's lungs, allowing blood to flow in more easily," Green said.