"It is not known why the results of the Handihaler and Respimat are so different, but [it] will give the FDA pause before approving the Respirat in this country," he said.
Another expert said Spiriva can have other serious side effects.
"While it's difficult to compare the different delivery systems' effect on mortality, it is known that certain patients with glaucoma or a history of urinary retention should not use this drug," said Dr. Len Horovitz, a pulmonary specialist at Lenox Hill Hospital in New York City. "It can also cause paradoxical bronchospasm, and severe allergic reactions. Tiotropium causes dry mouth, and can elevate heart rate. Since it is used in COPD, which is associated with cardiac conditions, other cardiac complications are possible."
Patients need to discuss the risks and benefits of COPD treatments with their doctors, Singh advised.
The study appears online June 14 in the BMJ.
COPD, the fourth leading cause of death worldwide, includes emphysema and bronchitis and is typically caused by decades of smoking.
The American Academy of Family Physicians has more about COPD.
-- Robert Preidt
SOURCES: Mark Rosen, M.D., director, pulmonary rehabilitation, North Shore University Hospital, Manhasset, N.Y. and Long Island Jewish Medical Center, New Hyde Park, N.Y.; Len Horovitz, M.D., pulmonary specialist, Lenox Hill Hospital, New York City; Johns Hopkins Medical Institutions, news release, June 14, 2011
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