The U.S. Food and Drug Administration said on Monday that product labels for three popular asthma medications have been updated to state that the drugs could increase the chance of severe asthma attacks that could result in death.

The warnings, first proposed last November, involve long-acting bronchodilator medicines Advair and Serevent, made by GlaxoSmithKline Plc, and Foradil from Novartis AG.

In a public health advisory issued on its Web site, the FDA said the inhaled drugs should only be used after other medicines, such as inhaled corticosteroids, fail to control asthma.