(The New York Times News Service) -- A large study on the popular asthma medication salmeterol was halted after researchers uncovered evidence that the drug may pose a slightly higher risk for respiratory and asthma-related deaths among black patients.

More commonly known by its brand name, Serevent, the drug is a member of the beta agonist class of asthma medications, which treat asthma symptoms by relaxing inflamed airways.

The report, published in the January issue of Chest, offers details of the research that was halted after the risk surfaced.

In 2003, that increased risk prompted the drug's manufacturer, GlaxoSmithKline, to strengthen its safety warnings on the labels of both Serevent and its corticosteroid-enhanced combination drug Advair.

"The bottom line is that, in a very large study in which salmeterol or a placebo was added to whatever treatment patients already were on, there was an increased number of severe asthma attacks, including fatal attacks," says study co-author Dr. Harold S. Nelson, a professor of medicine, allergy and immunology at the National Jewish Medical and Research Center in Denver.

"And I suspect that it's not actually ethnicity that is the issue," he adds, "but rather it's a situation where there's higher risk for people who perhaps have less access to medical care to begin with, or whose asthma was less well-controlled to begin with."

For the years 1996 to 2003, Nelson and his colleagues assessed the harmful side effects of salmeterol among more than 26,000 males and females over the age of 12. All the participants were asthma sufferers already taking some form of asthma medication other than inhaled beta antagonists. More than 70 percent were white, while 18 percent were black.

In the year before the study, more than a quarter of the patients had visited an emergency room due to an asthma incident, and 8 percent had been hospitalized. More than 60 percent reported having nighttime asthma at least once a week. Over a 28-week period, each patient was asked to use a salmeterol inhaler or a placebo inhaler twice daily as a supplement to their current drug regimen. Every four weeks, the patients reported any serious side effects.

Nelson and his associates report in Chest that white patients on either salmeterol or a placebo showed almost no difference in the number of life-threatening or fatal respiratory or asthma-related episodes.

In contrast, the numbers were significantly different among the black patients -- with about four times as many salmeterol patients reporting serious side effects.

The researchers noted, however, that the overall actual numbers of patients negatively affected was quite small -- amounting to less than 1 percent of the groups sampled.

They also pointed out that most of the imbalance in salmeterol and placebo patient outcomes occurred in the first year of the study, when the method for recruiting volunteers was based on an impersonal advertising system. In subsequent years, patients known and cared for by the researchers were brought into the study.

They suggested this might mean that patients whose asthma is being properly monitored are less likely to develop salmeterol complications.

This same rationale was proposed as a potential explanation for the higher risk the drug seems to pose to blacks -- with behavior perhaps playing a more important causal role than the drug itself.

The researchers noted, for example, that blacks reported less corticosteroid use and higher rates of hospitalization and emergency room visits due to asthma before the study started.

"It was very clear that African-Americans as a whole had less well-controlled asthma, so they were perhaps more susceptible to negative effects," Nelson says.

"In any case, it's probably true that these drugs should not be used except in combination with an inhaled steroid, because by themselves they control the symptoms, but they don't treat the underlying disease," he cautions.

"People should be using an inhaled steroid to alleviate the underlying disease," Nelson says. "Then there's no danger in using these drugs to help control the symptoms."

Dr. Adam Wanner, a professor of medicine at the University of Miami, views the study as valuable but inconclusive.

"I agree with Dr. Nelson, in that if you look at the results you cannot really say why there was a difference," he says. "Was it related to some genetic differences? One cannot conclude anything significantly. The interpretation is wide open."

In addition to receiving research funding from the company, Nelson is a consultant and speaker for GlaxoSmithKline. Similarly, all members of the research team are either consultants or direct employees of the company.

A second study in the same journal found that fish oil supplements may help prevent exercise-induced asthma.

The Indiana University researchers found that patients suffering from mild to moderate persistent asthma who took fish oil capsules on a daily basis for three weeks experienced significant improvements in their pulmonary function after exercise. Dependence on emergency inhalers also dropped.

Copyright 2006 The New York Times News Service. All rights reserved.