Which of the following is NOT a selective Beta-1 blocker?

• A. Betaxolol
• B. Timolol
• C. Atenolol
• D. Metoprolol

Answer: (B)

The main idea is receptor selectivity among beta-blockers. Beta-1 selective (cardioselective) blockers mainly block beta-1 receptors in the heart, reducing heart rate and contractility with fewer effects on the lungs. Betaxolol, atenolol, and metoprolol are examples of cardioselective agents. Timolol, however, blocks both beta-1 and beta-2 receptors, so it is not selective for beta-1. This non-selectivity means it can affect bronchial and vascular smooth muscle (β2 effects) as well as the heart. Timolol is commonly used topically for glaucoma, where systemic beta-blockade is less of a concern, but pharmacologically it is a non-selective beta blocker. Therefore, the drug that is not a selective Beta-1 blocker is timolol.