WASHINGTON — The government is issuing new restrictions on some widely used long-acting asthma drugs, saying they should never be used without other asthma controllers to prevent a lifethreatening risk.

Four medications — Foradil, Serevent, Advair and Symbicort — contain an ingredient that relaxes muscles in the lung’s airways. While they’re very helpful for some patients, the way they work also may mask symptoms that can trigger serious asthma attacks. It’s a particular concern for children.

The Food and Drug Administration ordered new labels saying the drugs should be used for the shortest possible duration — and only together with other medications such as inhaled steroids that work differently, by relieving airway inflammation.