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Friday, November 18, 2005

Viagra soothes the heart

Viagra soothes the heart
Impotence drug is rebranded to tackle fatally high blood pressure.

Charlotte Schubert


Easy bleeding: Viagra can loosen blood vessels in the penis and the lungs.
© Alamy
The little blue pill famous for enhancing love lives is now being used to treat the heart. Research showing how Viagra acts above the belt has put the pill on pharmacy shelves in a repackaged form, to help the sufferers of a devastating heart and lung condition.

Pulmonary arterial hypertension delivers its blow mainly to young women, killing about half of those afflicted within five years of diagnosis. The condition, which affects about 100,000 people worldwide, causes tiny blood vessels in the lungs to thicken and narrow, often for no apparent reason.

The lung damage puts huge pressure on the heart via the pulmonary artery, the big vessel that shunts blood from the heart to the lungs. Patients suffer from poor oxygenation of their blood, weakness and shortness of breath. They often die from heart failure.

"It's tragic to see a 32-year-old mom who can barely walk across the room," says David Kass, a cardiologist at Johns Hopkins University in Baltimore, Maryland. "Anything that can make these people feel better is a big deal."

Little white pill

Drugs currently prescribed for this disease can help patients live more comfortably but they cost some US$20,000 per year says Kass. Viagra (sildenafil citrate), famous for opening up blood vessels, provides a cheaper option.

On the back of a large trial, published in the New England Journal of Medicine1 this week by Nazzareno Galiè from the University of Bologna, Italy, Pfizer has repackaged the drug as Revatio. It has had the little white pill on drugstore shelves in the United States since July. This month the drug was approved for pulmonary arterial hypertension in Europe too.

Experts say the drug might help a wide variety of more common heart and lung troubles. Researchers are even investigating whether the pill could protect mountaineers from the potentially lethal effect on the heart of high altitude and low oxygen levels.

Rush of blood to the lungs

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When drug developers first invented Viagra they were looking for a treatment for common heart disease. The drug did not work too well for that, but male patients certainly seemed to enjoy the side effects.

The drug inhibits a specific enzyme, and this helps to dilate blood vessels in the penis, causing blood to rush in and enhancing an erection. The same enzyme also happens to be prevalent in the lung. Experts suspect that the drug dilates blood vessels in the lung and inhibits the growth of cells that block the blood vessels, enhancing blood flow and putting less pressure on the heart.

In Galiè's trial, 278 sufferers were given either Viagra pills or a placebo three times a day. After 12 weeks, the treated subjects had reduced pressure in their pulmonary artery and had more spring in their step. In a standard, six-minute walking test, subjects walked about 45 metres further than they did before the treatment.

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References

1. GalièN., et al. New England Journal of Medicine, 353. 2148 - 57 (2005).

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