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Three common asthma inhalers containing the drugs salmeterol or formoterol may cause up to 80 percent of asthma-related deaths, say researchers urging that they be taken off the market.

Asthma is a disease of the human respiratory system where the airways narrow, often in response to a "trigger" such as exposure to an allergen, cold air, exercise, or emotional stress.

Researchers led by Edwin Salpeter at Cornell and Stanford University studied records of 33,826 patients and found that patients who inhaled the long-acting beta-agonists salmeterol or formoterol were 3.5 times more likely to die from asthma and 2.5 times more likely to be hospitalised (whether or not death resulted), compared with those taking a placebo, a report posted in the university website said.

Although these medications relieve asthma symptoms, they also promote bronchial inflammation and sensitivity without warning, the researchers said.

The trade names of salmeterol is Serevent and Advair and both are made by GlaxoSmithKline. The trade name of formoterol is Foradil and it is made Novartis Pharmaceuticals.

Nevertheless, asthma death is relatively rare - 15 patients in the meta-analysis who were taking the beta-agonists died, compared with three in the placebo group - over a six-month period.

"In total, there are about 5,000 deaths a year due to asthma in the US, whether or not a person is taking a long-acting beta-agonist," Salpeter said.

"We can show that overall it is statistically significant that, compared to patients taking a placebo, these long-acting beta-agonists kill a lot of people," he said.

"These asthma deaths are generally in healthy young adults," said his daughter, Shelley Salpeter, the lead author of the paper appearing online and in the June 20 issue of Annals of Internal Medicine.

"We estimate that approximately 4,000 out of the 5,000 asthma deaths that occur in the US each year are actually caused by these long-acting beta-agonists, and we urge that these agents be taken off the market," she added.