## **Core Concept**
Long-acting beta 2 agonists (LABAs) are a class of bronchodilators used in the management of asthma and chronic obstructive pulmonary disease (COPD). They work by stimulating beta 2 receptors in the lungs, leading to bronchodilation. LABAs have a duration of action of at least 12 hours.

## **Why the Correct Answer is Right**
Salmeterol is a long-acting beta 2 agonist (LABA) used in the maintenance and control of asthma symptoms and in the treatment of COPD. It has a rapid onset of action but more importantly, its effects last for at least 12 hours, making it suitable for twice-daily dosing. Salmeterol works by binding to the beta 2 adrenergic receptor, activating adenylate cyclase, and increasing the levels of cyclic AMP in the cell, which results in smooth muscle relaxation and bronchodilation.

## **Why Each Wrong Option is Incorrect**
- **Option A:** is incorrect because it does not correspond to a recognized LABA.
- **Option B:** is incorrect because it does not correspond to a recognized LABA.
- **Option D:** is incorrect because it does not correspond to a recognized LABA.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that LABAs, such as salmeterol, should not be used as monotherapy in asthma; they are recommended to be used in combination with an inhaled corticosteroid (ICS) to control inflammation and prevent exacerbations.

## **Correct Answer:** .