**Core Concept**
Salmeterol is a long-acting beta-2 adrenergic receptor agonist (LABA) used in the management of asthma and chronic obstructive pulmonary disease (COPD). It works by stimulating the beta-2 receptors in the lungs, leading to bronchodilation and improved lung function.

**Why the Correct Answer is Right**
Salmeterol is not effective for acute asthmatic attacks because it has a slow onset of action, taking around 30 minutes to 1 hour to produce significant bronchodilation. This slow onset of action makes it unsuitable for use in acute asthma exacerbations, where rapid relief of symptoms is essential. In contrast, short-acting beta-2 agonists like salbutamol are preferred for acute asthma attacks due to their rapid onset of action.

**Why Each Wrong Option is Incorrect**
**Option A:** Regular use of salmeterol may actually improve asthma control and reduce symptoms, rather than worsening asthma. This is because it helps to maintain airway patency and prevent bronchospasm.
**Option B:** Salmeterol was indeed the first long-acting selective beta-2 agonist to be introduced, making it a landmark development in asthma management.
**Option D:** Salmeterol is actually less beta-2 selective than salbutamol, as it has a higher affinity for beta-1 receptors. This is a potential drawback of salmeterol, as beta-1 receptor stimulation can lead to cardiac side effects.

**Clinical Pearl / High-Yield Fact**
It's essential to remember that LABAs like salmeterol should not be used as monotherapy in asthma patients. Instead, they should be used in combination with an inhaled corticosteroid (ICS) to reduce the risk of exacerbations and improve lung function.

✓ Correct Answer: C. Effective for acute asthmatic attacks