Viagra may help children with fatal lung disorder

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Physicians at The Hospital for Sick Children (SickKids) have found that the drug sildenafil, also known as Viagra, may help children suffering from pulmonary arterial hypertension. This research is reported in the June 14, 2005 issue of Circulation: Journal of the American Heart Association.

In a small pilot study, sildenafil was administered for one year to 14 children with pulmonary arterial hypertension, aged five to18 years old. Results showed an increase in exercise capacity and improved breathing among patients. After 12 months, the average distance walked in six minutes was increased by 154 meters (508 feet). As well, resistance in the pulmonary arteries dropped by about 20 per cent, allowing the children to breathe easier.

“Sidenafil compares favorably to other drugs used to treat pulmonary arterial hypertension, with the added benefit of improving symptoms among patients, including increased mobility and improved breathing,” said the study’s lead author Dr. Tilman Humpl, head of the Pulmonary Hypertension Clinic and critical care cardiologist at Sick Kids and an assistant professor of Paediatrics at the University of Toronto. “It has far fewer side effects than other treatments and is less of a burden on a child trying to manage with this difficult and complex condition.”

Pulmonary arterial hypertension is a condition in which blood pressure in the arteries that supply the lungs is extremely high. The small blood vessels in the lungs become progressively narrower and their walls thicken, so they can’t carry as much blood, causing pressure to build and back up. If the pressure soars high enough, the heart can’t keep up, causing fatigue, dizziness, shortness of breath and eventually heart failure and death. Pulmonary arterial hypertension can be inherited, caused by a congenital heart defect or result from another chronic heart or lung disease.

“Untreated, children usually die within one year of diagnosis,” said Dr. Ian Adatia, the study’s principal investigator and now an associate professor of Pediatrics at the University of California San Francisco Children’s Hospital. “And even with the current best therapy, continual intravenous infusion of the drug prostacyclin, which helps lower the pressure in the pulmonary arteries, few patients live five years past diagnosis.

Prostacyclin is often used to treat the condition but can be disruptive for a child’s routine as they must always carry an infusion pump and parents are required to mix the drug daily. There are also many unpleasant side effects, including jaw and muscle pain and facial flushing.

In searching for an alternative treatment, researchers looked at sildenafil as an option. When used to treat erectile dysfunction, the drug relaxes the smooth muscle of blood vessels, expanding the blood vessels and increasing blood flow. Similarly, the study found that sildenafil helped children with pulmonary arterial hypertension, by allowing the blood vessels to expand, which prevents the small blood vessels from narrowing, thereby improving a child’s symptoms of the condition. Patients on sildenafil had a 100 per cent survival rate after one year, whereas similar patients not on the drug had a survival rate of about 37 per cent at one year. However, deaths occurred in the second year of treatment and a longer-term study is necessary to define sildenafil’s place in chronic therapy.

“The next step is to confirm these results in a larger randomized, controlled trial, comparing sildenafil against placebo or other pulmonary arterial hypertension drugs,” added Dr. Humpl.

The study was conducted while Dr. Adatia was head of the Pulmonary Hypertension Clinic at SickKids, and he collaborated with Dr. Humpl, current head of the clinic, Janette Reyes, Helen Holtby and Derek Stephens, all from SickKids.

The study was funded by Pfizer, Inc.

The Hospital for Sick Children, affiliated with the University of Toronto , is Canada’s most research-intensive hospital and the largest centre dedicated to improving children’s health in the country. Its mission is to provide the best in family-centered, compassionate care, to lead in scientific and clinical advancement, and to prepare the next generation of leaders in child health.