One of the drugs used in inhalers to treat asthma can counteract the benefits of the others, U.S. researchers reported Tuesday.
The finding may explain why some patients who use the inhalers actually get worse over time, the researchers at the University of Pittsburgh School of Medicine said.
The ingredient is albuterol, in a class of medications called beta-agonists. In inhalers it is combined with steroids to open airways and ease the gasping of patients with asthma and other lung diseases.
But in a report presented to the annual meeting of the American Academy of Allergy, Asthma and Immunology in San Francisco, the researchers said a bad form of albuterol can accumulate in the body and worsen symptoms instead of helping.
Sometimes these patients end up in emergency rooms, said Williams Ameredes, an assistant professor of cell biology and physiology who led the study.
The trouble, said Ameredes, is that albuterol has two forms or isomers — a so-called left-handed version and a right-handed one. These isomers refer to the molecular structure.
The “right” version relaxed the airways when used with the steroid dexamethasone but the “left” version in fact increased the inflammatory signals that caused the airways to tighten, he said.
“One potential explanation is that long-term repeated usage of albuterol may result in accumulation of the (left) isomer of albuterol, which we know persists in the body three to four times longer than the beneficial (right) isomer, which is normally metabolized in about three hours,” Ameredes said in a statement.
It is now possible to make a version of albuterol that contains only the beneficial, right-handed isomer, Ameredes said, and drug companies should examine this possibility.
