Patients with asthma and chronic obstructive pulmonary disease who regularly use a beta-agonist have a greater than two-fold higher cardiac risk for events including myocardial infarction than patients on placebo, according to a meta-analysis in the June issue of CHEST. The American research team analyzed 13 single-dose trials and 20 longer-duration trials.

"If you want to push continuous use of beta-agonists, you'll find plenty of published studies to back your point of view," Shelley Salpeter, MD, and lead author of the study, said. "However, because of their flawed study designs, none of these trials were truly placebo-controlled and therefore should not be used to make valid conclusions about the safety of beta-agonists. We worry that physicians who recommend regular use of beta-agonists may actually be putting their patients at risk."

In the article, the authors noted that they excluded from analysis the large number of trials that allowed patients in the placebo group to use beta-agonists on an as-needed basis while retaining them in the placebo group for later analysis.

The authors were surprised to find beta-agonist use in patients with asthma and chronic obstructive lung disease increased the risk for adverse cardiac events by over two-fold compared to placebos. They wrote that initiation of beta-agonist use in patients with chronic obstructive pulmonary disease results in increased heart rate and reduced potassium concentrations (compared with placebo). They speculate that these mechanisms and others associated with beta-adrenergic stimulation may trigger ischemia, congestive heart failure, arrhythmias, and sudden cardiac death.