A patient on timolol eye drops for glaucoma develops worsening of bronchospasm. The ophthalmologist switches to betaxolol. The rationale is that betaxolol is which of the following?

• A A selective alpha-2 agonist with no bronchial effects
• B A non-selective beta blocker with additional alpha-blocking properties
• C A carbonic anhydrase inhibitor unrelated to adrenoceptors
• D A selective beta-1 blocker with lower affinity for bronchial beta-2 receptors ✓

Explanation

Betaxolol is a cardioselective (beta-1 selective) adrenergic blocker. In the eye, it reduces aqueous humor production by blocking beta-1 receptors in the ciliary epithelium, similar to timolol, but its lower affinity for beta-2 receptors in bronchial smooth muscle makes it safer in patients with obstructive airway disease. However, selectivity is relative and not absolute, so caution remains. Timolol is a non-selective beta blocker.

Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.