Reducing blood pressure in the lungs. (Biomedicine).

High pressure in the blood vessels supplying the lungs can strain the heart and eventually cause heart failure. People with this condition, called pulmonary hypertension, often tire so easily that they can hardly move. Conventional drugs that lower blood pressure are ineffective in alleviating the lung condition, and the only drug that works requires constant intravenous infusion. A new study suggests that a new drug, bosentan, may offer the first oral therapy for people with pulmonary hypertension.

An international research team gave 21 people with pulmonary hypertension daily doses of bosentan and provided 11 others with a placebo. After 12 weeks, the patients treated with bosentan could walk an average of 230 feet further in 6 minutes than they could at the beginning of the study. In contrast, those people given a placebo walked 20 feet less in 6 minutes than they did at the beginning of the study.

Increased endurance "is a big benefit in these patients," says lead researcher Richard N. Channick of the University of California, San Diego. He and his colleagues report their results in the Oct. 6 LANCET.

Bosentan blocks the effects of endothelin, a naturally occurring chemical in the body that constricts blood vessels and increases blood pressure. People with pulmonary hypertension tend to have higher-than-normal concentrations of endothelin in their blood.

An unpublished study of 100 people confirmed the effects of bosentan, Channick says. Those results were presented to an advisory panel of the Food and Drug Administration. The panel recommended that the drug be approved, but the FDA has yet to make its final decision. --D. C.