## **Core Concept**
The question tests knowledge of β2 agonists used in asthma management, specifically those administered via inhalation. β2 agonists are bronchodilators that relax bronchial smooth muscles, making them easier to breathe through. They are crucial in both the relief of acute asthma symptoms and the long-term control of asthma.

## **Why the Correct Answer is Right**
The correct answer, **Salmeterol**, is a long-acting β2 agonist (LABA) that is administered via inhalation. It is particularly noted for its suitability in twice-daily prophylaxis due to its long duration of action. Although LABAs like salmeterol are not typically the first choice for terminating acute asthma attacks due to their slower onset of action compared to short-acting β2 agonists (SABAs) like albuterol, salmeterol's properties make it effective for long-term control. However, for immediate relief during acute attacks, SABAs are preferred.

## **Why Each Wrong Option is Incorrect**
- **Option A:** This option is incorrect because it does not specify a known β2 agonist suitable for both acute relief and long-term control via inhalation.
- **Option B:** This option might refer to a short-acting β2 agonist, which is effective for terminating acute asthma attacks but not suitable for twice-daily prophylaxis due to its shorter duration of action.
- **Option D:** This option could refer to another medication not primarily used for both acute termination and prophylaxis of asthma via inhalation.

## **Clinical Pearl / High-Yield Fact**
A key point to remember is that while LABAs like **salmeterol** are excellent for long-term control of asthma symptoms, they should not be used as monotherapy for asthma. Instead, they are often used in combination with inhaled corticosteroids (ICS) for patients whose asthma is not adequately controlled with ICS alone. This combination enhances lung function and reduces symptoms more effectively than either medication alone.

## **Correct Answer:** . Salmeterol