Feb. 6 (HealthDay News) -- Schering-Plough's Asmanex Twisthaler, an inhaled steroid designed to prevent asthma attacks, has been approved by the U.S. Food and Drug Administration for children as young as 4 years, the Associated Press reported.

In March 2005, the drug was approved to prevent asthma attacks in adults and children aged 12 and older. The newly approved dose for youngsters is half the adult dose, the AP said.

Asthma is the most common chronic condition among children, affecting as many as 10 percent of Americans under 18. It's responsible for more than 14 million missed school days and close to 1 million visits to the emergency room each year, the wire service said, citing the Asthma and Allergy Foundation of America.

The Twisthaler doesn't have a propellant, but is inhaled when a user places the device in the mouth and breathes.

As with other corticosteroid inhalers, Asmanex has possible adverse effects including stunting a child's growth rate, causing oral fungal infections, and increasing users' risks of glaucoma or cataracts. More frequent side effects may include headache, sore throat, respiratory infection, upset stomach, and pain of the muscles, bones and back, according to AP.