Why should non-selective beta-blockers be avoided in patients with asthma?

Non-selective beta-blockers should be avoided in patients with asthma primarily because they can lead to airway contraction and trigger an asthma attack. This occurs because non-selective beta-blockers inhibit both beta-1 and beta-2 adrenergic receptors. While beta-1 receptors are mainly found in the heart, beta-2 receptors are located in the bronchial smooth muscles and are responsible for relaxing these muscles and dilating the airways. Inhibition of beta-2 receptors by non-selective beta-blockers can cause bronchoconstriction, which is detrimental for individuals with asthma, as it can exacerbate their condition and lead to significant respiratory distress.

Understanding this mechanism is crucial for managing asthma. Patients with asthma typically rely on medications that agonize beta-2 receptors, such as bronchodilators, to keep their airways open. Therefore, the use of non-selective beta-blockers can be counterproductive and may pose a serious risk for those with reactive airways.