The proportion of children who used a prescribed controller drug to treat their asthma doubled from 29 percent in 1997 - 1998 to 58 percent in 2007 - 2008, according to the latest News and Numbers from the Agency for Healthcare Research and Quality.

Asthma controller drugs, such as cortisteroids, control inflammation thereby reducing the likelihood of airway spasms; asthma reliever drugs, such as short-acting beta-2-agonists, make breathing easier; and leukotrienes help prevent asthma symptoms from occurring.

AHRQ also found that during the 1997 - 1998 and 2007 - 2008 timeframes:

-- Use of inhaled corticosteroids, a type of controller drug increased from 15.5 percent to 40 percent. Use of other controller drugs also increased: beta agonists (from 3 percent to 13 percent); and leukotriene (from 3 percent to 34 percent).

-- Use of reliever and oral corticosteroid drugs declined from 44 percent to 30 percent and from 17 percent to 9 percent, respectively.

-- Average annual total spending for all asthma drugs more than quadrupled from $527 million to $2.5 billion. Specifically, spending for controller drugs grew from $280 million to $2.1 billion and for reliever drugs, the increase was $222 million to $352 million (all in 2008 dollars).

-- Spending for oral corticosteroids fell from $25 million to $8 million (2008 dollars).