A University of Florida (UF) study has provided additional evidence that an antibacterial agent added to some asthma medications can cause airway constriction, making symptoms worse rather than better.

The chemical, benzalkonium chloride or BAC, is added to some albuterol medications taken by a device called a nebulizer. The nebulizer is commonly used in children under six years of age. The chemical is not used in the albuterol taken by metered-dose inhaler, the device typically used by older children and adults.

UF College of Pharmacy researchers found that 10 of 18 adults with asthma experienced a significant drop in breathing capacity when exposed to the preservative during their experiment. They published findings from their study in the January issue of the Journal of Allergy and Clinical Immunology.

The researchers warned parents and health care professionals not to use products that contain BAC.

"We suggest that it's illogical to use a preservative that may counteract the effect of albuterol -- the main medicine that you have to reverse an asthma attack," said Dr. Michael J. Asmus, an assistant professor of pharmacy practice and lead author of the journal article. He continued, "... the potential is that people having asthma attacks won't get relief from their rescue medicine, possibly leading to the need for hospitalization and aggressive treatment."

The UF research is the latest experiment to show the airway constriction effects of BAC. Richard Beasley of the Wellington School of Medicine first described problems with BAC in studies in the 1980s, yet it continued to be added to the drug.

In the UF experiment, research participants were given up to four 600 microgram doses of BAC, spaced 20 minutes apart. The idea was to mimic the maximum amount of BAC patients would inhale in an albuterol nebulizer solution under emergency department guidelines for reversing an acute asthma attack.

After inhaling one dose, three participants experienced more than a 20% drop in their ability to force air out of their lungs, while seven others -- including one whose capacity dropped 47% -- showed such declines after the second or third dose. So that the research participants' safety would not be endangered, no further doses of BAC were given once a 20% drop was observed. At that level, people begin to sense chest discomfort.

The authors noted that they have not tested a combination of albuterol and BAC, so it's not clear precisely how much the medicine's effectiveness would be limited by the additive.

"There have been case reports, however, of the medicine not working at all in some people," said Dr. Leslie Hendeles, a UF professor of pharmacy practice and a clinical pharmacist in the College of Medicine's pediatric pulmonary division. "When such patients have been given albuterol with BAC, their asthma attacks have just gotten worse."

The U.S. market for asthma medications is huge and growing as the number of people with the lung disease continues to climb. An estimated 17 million people have asthma, according to the American Lung Association.

Dr. Hendeles said that the U.S. Food and Drug Administration has shown no interest in asking or requiring companies to remove BAC from their products.

"It has not been easy to get attention to this issue because it can be difficult to determine whether patients in the midst of an asthma attack are failing to respond to treatment because their asthma is so severe or because the treatment itself is compromised by the presence of BAC," Hendeles stated.

The UF researchers are seeking to spread the word to physicians, nurses, pharmacists and parents about the possibility that BAC can limit the effectiveness of albuterol or even worsen an attack. If BAC is present in a medicine, manufacturers must list it on the label but do not have to indicate the amount.

SOURCES: "Antibacterial agent in some asthma medications linked to airway constriction, UF scientists find," University of Florida, Media Release, January 17, 2001.