Which of the following is a common short-acting beta agonist (SABA)?

Levalbuterol is identified as a common short-acting beta agonist (SABA) because it is specifically designed to quickly relieve bronchospasm associated with conditions like asthma and chronic obstructive pulmonary disease (COPD). SABAs are known for their rapid onset of action, typically within minutes, and they provide short-term relief from acute symptoms. Levalbuterol is the active isomer of albuterol, another commonly used SABA, and it works by stimulating beta-2 adrenergic receptors in the airway smooth muscle, leading to bronchodilation.

In contrast, other options listed are not classified as SABAs. Salmeterol and formoterol are long-acting beta agonists (LABAs), which provide extended relief and are used for chronic management of respiratory conditions rather than immediate relief. Montelukast is a leukotriene receptor antagonist, which functions differently by reducing inflammation and bronchoconstriction but does not act as a bronchodilator in the same way that SABAs do. Therefore, levalbuterol stands out as the correct answer in the context of common short-acting beta agonists.