The U.S. Food and Drug Administration said Tuesday that data submitted by the German drug maker Boehringer Ingelheim show a slightly higher rate of stroke for patients using its Spiriva Handihaler, an inhaler used to treat chronic obstructive pulmonary disorder (COPD), compared with a placebo.

Pfizer Inc. also markets Spiriva. A possible retreat from the market of Spiriva may provide a boost for GlaxoSmithKline Pls’s top-seller Advair.

"Potential safety concerns over Spiriva could facilitate earlier Advair use in less severe patients," Morgan Stanley analysts wrote in a note, according to Reuters.

The FDA’s Web site said Boehringer Ingelheim submitted the results of 29 studies involving Spiriva, which showed a slightly higher rate of stroke among patients treated with Spiriva compared to those not receiving the drug. The trials included about 13,500 COPD patients.

“Based on data from these studies, preliminary estimates of the risk of stroke are eight patients per 1,000 patients treated for one year with Spiriva, and six patients per 1,000 patients treated for one year with placebo. This means that the estimated excess risk of any type of stroke due to Spiriva is two patients for each 1,000 patients using Spiriva over a one-year period,” the FDA said on its Web site.

The health agency said it has requested additional information from the company and is reviewing post-marketing adverse events reported to FDA involving Spiriva.

More data are expected when the results of a large, four-year randomized trial called UPLIFT (Understanding the Potential Long-Term Impacts on Function with Tiotropium) are reported Those data are expected to be released in June. The FDA said it planned to analyze the UPLIFT data ad “communicate its conclusions and recommendations to the public.”

Meanwhile, “patients should not stop taking Spiriva HandiHaler before talking to their doctor,” the FDA said.

The FDA approved Spiriva in 2004. More than eight million patients worldwide have been treated with Spiriva, according to Boehringer Ingelheim.