In people who suffer from COPD, a progressive lung disease that makes it hard to breathe, adding an inhaled steroid to a so-called "long-acting beta-2 agonist" may do more harm than good, new research hints.

The benefit of the two-drug approach in COPD is limited, and furthermore, it's accompanied by substantial risks of pneumonia and other infections, the research team reports.

Still, current guidelines recommend this combination for reducing exacerbations in patients with severe and very severe COPD, Dr. Gustavo J. Rodrigo, from Hospital Central de las Fuerzas Armadas in Montevideo, Uruguay, and his associates point out in the October issue of the journal Chest.

Two examples of drugs that contain only a long-acting beta-2 agonist, or LABA, are Serevent and Foradil. Two examples of drugs that contain both a LABA and an inhaled steroid are Advair and Symbicort.

In a large systematic review, Rodrigo and his colleagues compared the safety and efficacy of regular use of the two agents with that of regular use of a LABA alone.

Their literature search turned up 18 randomized controlled trials involving 12,446 stable patients with moderate-to-very severe COPD.

In the pooled analysis, combination therapy was associated with a significantly reduced risk of moderate COPD flare ups compared with LABA-only therapy (17.5 percent vs 20.1 percent).

Combined treatment had no effect on the incidence of severe COPD exacerbations, however.

Moreover, compared with the single-drug approach, the two-drug approach produced significantly greater improvements in lung function and health-related quality-of-life.

The authors emphasize, though, that "the size of these benefits did not reach the suggested clinically important minimal differences."

The investigators also found that adding inhaled steroids to the treatment regimen significantly increased patients' risk of developing pneumonia (by 63 percent), viral respiratory infections (by 22 percent), and fungal infections in the mouth (by 59 percent).

And the two-drug approach did not reduce overall death rates compared with single-drug therapy.

For now, Rodrigo and associates conclude, "it's likely" that most patients with COPD with these levels of severity should be treated only with a LABA — at least until future research identifies which COPD patients are likely to benefit from inhaled steroids.