NEW YORK (Reuters Health) - In 2006, the Centers for Disease Control and Prevention (CDC) were notified of an increase in the number of blood stream infections associated with treprostinil (Remodulin), used to treat severe pulmonary arterial hypertension.

Prostanoid drugs act as vasodilators and antiproliferative agents, Dr. R. Barst and associates explain in the Morbidity and Mortality Weekly Report for March 2. Only two prostanoids are approved for use in the US, epoprostenol (Flolan) and treprostinil.

The CDC supervised a retrospective investigation for 2003 to 2006 to determine the relative rates of bloodstream infections among patients at seven treatment centers that care for patients with pulmonary arterial hypertension.

According to Dr. Barst, from the New York City Department of Health and Mental Hygiene, and colleagues, bloodstream infection rates were calculated as the number of infections per 1,000 days on which an IV prostanoid was administered. The pooled mean incidence rates were 1.11 per 1000 medicine days versus 0.43 per 1000 days, respectively.

The authors note that 26 different bacterial organisms were identified by blood cultures. Patients treated with treprostinil were more likely to harbor a gram-negative bacterium, which are notoriously difficult to treat. Moreover, two patients treated with treprostinil died.

In an editorial note, personnel at the CDC point out that treprostinil is far easier to use than its counterpart. It has a half-life of approximately 4 hours and does not require refrigeration. Epoprostenol is reconstituted at home and must be kept cool once mixed; its half-life is approximately 3 to 6 minutes.

The editorialists point out that 10 partially used vials of treprostinil from affected patients were sterile when cultured, and because of the variety of bacterial organisms involved, they discount intrinsic contamination of treprostinil or its diluents as a cause of the infections.

They call attention to the fact that epoprostenol is dispensed in single-use vials, whereas treprostinil is supplied in a 30-day multiple-dose vial, and thus is more subject to contamination. Other possibilities are variability in infection-control practices, or differences in the drugs' anti-inflammatory activity.

The authors calculate that one blood stream infection would occur every 2.5 years for a patient receiving IV treprostinil, and every 6.4 years if treated with epoprostenol.

Until further information is available, "clinicians should advise patients about the potential advantages and disadvantages of both drugs and assist patients in choosing medication that best suits their clinical situation," the editorialists write. They also advise health-care providers to routinely review with their patients infection-control practices.