(RxWiki News) Medications used to treat erectile dysfunction may have another use. These medications may provide a way to help young boys with a disabling genetic disease.
Tadalafil (Cialis) and sildenafil (Viagra) have shown promise in early research at improving blood flow to the muscles of boys with Duchenne muscular dystrophy.
Duchenne muscular dystrophy (DMD) is a genetic disorder that affects about one of every 3,600 boys. Children born with DMD have progressive muscle degeneration that usually leads to death by the age of 25.
"If your son has Duchenne muscular dystrophy, discuss treatment options with your pediatrician."
This research was led by Michael D. Nelson, PhD, of Cedars Sinai Medical Center in Los Angeles, California.
Based on animal research that suggested erectile dysfunction medications might be useful, Dr. Nelson and colleagues enrolled 10 boys with DMD and 10 healthy age-matched male controls (comparisons) between 2012 and 2013. The boys were aged 10 to 13.
In DMD, the body does not make the protein called dystrophin, which helps maintain healthy muscles. In DMD, muscles are deprived of nitric oxide, and blood flow to the muscles during exercise is restricted. The medications tadalafil and sildenafil act to inhibit the enzyme called phosphodiesterase type 5 (PDE-5), increasing blood flow.
The boys with DMD were all on steroids to help with their disease, and five of the 10 were also on cardiac medication, as the disease affects the muscle of the heart.
The blood flow in all of the participants' muscles was measured when they were at rest and when they were doing a handgrip exercise.
Dr. Nelson and team found that the boys with DMD had impaired blood flow to their muscles prior to receiving the study medications.
The boys with DMD were given either tadalafil or sildenafil one to three hours before the exercise, depending on when each medication is thought to work best. These boys received doses according to their weight. After two weeks, the boys came back to redo the test but received whatever medication they did not get the first time.
Both medications were found to work equally well. PDE5 inhibition normalized the exercise-induced increase in skeletal muscle blood flow (measured by Doppler ultrasound), which was markedly blunted in boys with DMD, according to the authors.
After taking either medication, the boys' blood flow response during exercise was the same as that of the boys who were healthy.
"The effect was immediate and dramatic. The result also was more pronounced with higher doses," said study co-author Ronald G. Victor, MD, assistant director of the Cedars-Sinai Heart Institute, in a press release.
Dr. Ryan Coates, a pediatric neurologist at Loyola Medical Center in Chicago, said he sees many patients with DMD, and that there are very few treatment options, so he's pleased to see medications being tested that show promise.
"I think it looks exciting," Dr. Coates told dailyRx News. However, he said 10 patients is a very small study, and the patients were not followed for any length of time.
"We need more long-term evidence that this might be helpful and to see if the drug creates problems or if the body acclimates to the drug," he said. "I would want to see longer studies before I'd put my patients on it."
Dr. Nelson and colleagues noted that their study did not address whether the medications would work over a sustained amount of time. Also, “this proof-of-concept study does not address the crucial question of whether restoring normal blood flow regulation will preserve dystrophic skeletal muscle and slow disease progression,” the authors wrote.
This study appeared online May 7 in Neurology.
Some of the authors disclosed being consultants for the pharmaceutical company Eli Lilly and Company (manufacturer of Cialis) after they collected and analyzed data for this study.
