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

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

**Core Concept:** Cardioselective beta blockers are a class of drugs that preferentially inhibit beta-1 receptors in the heart, sparing beta-2 receptors in the lungs and peripheral tissues. This results in fewer side effects compared to non-selective beta blockers.

**Why the Correct Answer is Right:** D. Carvedilol is a cardioselective beta blocker because it selectively inhibits beta-1 and alpha-1 receptors, providing both beta-blocking and alpha-blocking actions. This dual action makes it effective in treating hypertension, heart failure, and angina.

**Why Each Wrong Option is Incorrect:**

A. Atenolol is a cardioselective beta blocker, inhibiting beta-1 receptors in the heart and beta-2 receptors in the lungs and peripheral tissues.
B. Metoprolol is also a cardioselective beta blocker, inhibiting beta-1 receptors in the heart and beta-2 receptors in the lungs and peripheral tissues.
C. Propranolol is a non-selective beta blocker, inhibiting both beta-1 and beta-2 receptors in the heart and peripheral tissues. This results in more side effects compared to cardioselective beta blockers.

**Clinical Pearl:** Cardioselective beta blockers are preferred over non-selective beta blockers due to reduced side effects. This distinction is crucial in understanding drug selection for patients with heart conditions, as the choice of beta blocker influences treatment outcomes and patient safety.