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TUESDAY, March 23 (HealthDayNews) -- An inactive ingredient found in some asthma inhalers may be counteracting the beneficial effect of steroids, which are often given to people with the breathing disorder.

If validated by future studies, this finding, which was done with cell cultures in a laboratory, may explain why some people have the paradoxical effect of getting worse, instead of better, when they use inhalers.

"Some patients can have wheezing or bronchodilation, which is what it [an inhaler] is designed to prevent or relieve," says Dr. Clifford W. Bassett, an allergist and asthma specialist at New York University Medical Center in New York City.

The research is to be presented March 23 at the annual meeting of the American Academy of Allergy, Asthma and Immunology in San Francisco.

Albuterol, one of a class of drugs called beta-agonists, is often given in combination with steroids to treat asthma and other lung diseases. It works by relaxing and opening the muscle surrounding air passages in the lungs.

"The key is that albuterol is really the sum of multiple parts," explains Dr. Michael Marcus, director of pediatric pulmonology, allergy and immunology at Infants and Children's Hospital of Brooklyn at Maimonides in New York City.

"Biochemically, the end result isn't usually a single chemical but a racemic mixture," he adds. In other words, albuterol has two components, an S-isomer and an R-isomer. The R-isomer is the active component, and it was originally thought that the S-isomer, which is inactive, had no effect on people using inhalers.

In fact, this may not be the case, according to the new study. "As they're able to separate the molecules and test the effects independently, what we've learned now is that the S molecule has significant activity and actually mimics the disease of asthma," Marcus says.

The new research, led by Bill T. Ameredes, co-director of the Asthma, Allergy and Airway Research Center at the University of Pittsburgh Medical Center, looked at the effect of the different isomers on the smooth muscle cells of the human airway. Specifically, the researchers wanted to see if the isomers enhanced or counteracted the anti-inflammatory effects of a steroid given simultaneously.

As it turned out, the R-albuterol in combination with the steroid dexamethasone reduced the production of a key inflammation-producing chemical signal in the airway muscle. This accentuated the anti-inflammatory effects of the steroid. That's the good news.

The unfortunate news is that the S-albuterol increased production of the same signal, effectively nullifying the other effects. "The suppression that we normally would get from steroids, that effect was nullified to a large degree," Ameredes explains.

Still, the study is a preliminary one. "We have to keep in mind that this is an initial study and that it was performed in a cell culture model so it wasn't a study that was actually performed in humans," Ameredes says. "But it gives us an indication that perhaps we need to give some further consideration to the fact that these S-isomers may not be in fact inert but may be producing responses, many of which are unknown but some of which may be counterproductive."

A version of the therapy with only the active ingredient is already available but, Ameredes says, is only available in a nebulized form. "My understanding is that it's used with quite good effect in emergency rooms, in terms of having it in an inhaler form," he says. "It is not available on market yet but I've heard that it is on the way."

More information

The American Academy of Allergy, Asthma and Immunology has more information on asthma medications and on asthma management.

(SOURCES: Bill T. Ameredes, Ph.D., assistant professor, medicine, University of Pittsburgh School of Medicine, and co-director, Asthma, Allergy and Airway Research Center, University of Pittsburgh Medical Center; Clifford W. Bassett, M.D., allergist and asthma specialist, New York University Medical Center, New York City; Michael Marcus, M.D., director, pediatric pulmonology, allergy and immunology, Infants and Children's Hospital of Brooklyn at Maimonides, New York City; March 23, 2004, presentation, annual meeting, American Academy of Allergy, Asthma and Immunology, San Francisco)

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