When using a nonselective β agonist, what adverse effect should be anticipated?

Using a nonselective β agonist typically stimulates both β1 and β2 adrenergic receptors. The activation of β1 receptors, primarily found in the heart, leads to an increase in heart rate and contractility, which can result in tachycardia. This is a common adverse effect of nonselective β agonists, as they enhance the heart's response to sympathetic stimulation.

In contrast to selective β agonists, which may primarily target either the heart or the lungs, nonselective β agonists do not have this specificity, thus increasing the likelihood of cardiovascular side effects. For instance, while the stimulation of β2 receptors in the lungs may be beneficial for bronchial dilation, the systemic effects of β1 receptor stimulation can cause significant changes in heart rate.

The other options, such as bradycardia, hypotension, and worsening bronchoconstriction, are not typical adverse effects associated with nonselective β agonists. Instead, nonselective β agonists are more likely to contribute to increased heart rate rather than a decrease or other cardiovascular instability. Therefore, tachycardia is the most anticipated adverse effect when using a nonselective β agonist.