**Question:** Which of the following is not a cardioselective β-blocker:

A. Atenolol
B. Metoprolol
C. Propranolol
D. Carvedilol

**Core Concept:**

A cardioselective β-blocker is a type of medication that preferentially inhibits β1-adrenergic receptors in the heart, sparing other β-receptors in the body. This results in reduced heart rate and contractility while minimizing the side effects on non-cardiac tissues, like bronchi and skin.

**Why the Correct Answer is Right:**

Drug D, Carvedilol, is a non-selective β-blocker, meaning it inhibits both β1 and β2 receptors, leading to more significant side effects in bronchial and cutaneous tissues. Non-selective β-blockers can lead to bronchospasm, worsening asthma, and skin reactions like pruritus and rash.

**Why Each Wrong Option is Incorrect:**

Atenolol (Option A) is a cardioselective β1-blocker, which is advantageous for patients with heart disease as it reduces heart rate and contractility without significant effects on bronchial or skin tissue.

Metoprolol (Option B) is also a cardioselective β1-blocker, resulting in similar advantages and disadvantages as atenolol.

Propranolol (Option C) is a non-selective β-blocker, leading to the side effects mentioned above.

**Clinical Pearl:**

Understanding the selectivity of β-blockers is crucial when treating patients with heart conditions, as cardioselective agents like atenolol and metoprolol are preferred over non-selective agents like propranolol and carvedilol for their reduced side effects on non-cardiac tissues.