NEW YORK, Feb. 26 -- Shares of United Therapeutics traded heavily Monday as the market reacted to scientific data affecting the Silver Spring drugmaker's lead product, Remodulin.

On Friday, the Scientific Leadership Committee of the Pulmonary Hypertension Association recommended that doctors "be mindful" of the range of infections in patients being given long-term infusions through a catheter of drugs known as prostacyclins. United Therapeutics sells the prostacyclin treprostinil under the trade name Remodulin.

The warning came in reaction to a recent presentation by the Centers for Disease Control and Prevention that said that a higher rate of infections had been seen in patients given treprostinil intravenously, compared with patients given another type of prostacyclin called epoprostenol, marketed by GlaxoSmithKline under the trade name Flolan.

The pulmonary group called the CDC's presentation a "hypothesis generating report which does not permit definitive or specific conclusions at this time," suggesting that more studies were needed.

Both drugs treat pulmonary hypertension, which is high blood pressure in the blood vessel that leads from the heart to the lungs.

United Therapeutics shares opened at $54.85 yesterday, down 5.1 percent from Friday's close of $57.78, but closed at $58.53.

Shares of GlaxoSmithKline closed 1 cent lower, at $56.91, on the New York Stock Exchange.

Andrew Fein, an analyst at CE Unterberg Towbin, expressed concern that the CDC data could pose a threat to Food and Drug Administration's approval of two other forms of Remodulin, an inhalable version and an oral version, currently in development.

Andrew Fisher, a United Therapeutics spokesman, confirmed that the company had enrolled about 175 of its targeted 200 patients for a clinical trial to test its inhaled form of Remodulin and had started enrolling patients in a clinical trial for an orally taken form of the drug in October.

United Therapeutics said Monday it will work closely with the pulmonary group to improve patient care using Remodulin, and that it planned to begin a clinical study on rates of infection in patients given prostacyclins through an intravenous tube.

The company also said it planned to revise labeling for Remodulin to better describe the risk of infection.

Remodulin sales accounted for most of United Therapeutics' $159.6 million of revenue in 2006.