A patient on long-term topical timolol maleate 0.5% eye drops develops worsening dyspnea and bradycardia. This systemic effect is best explained by:
- A Local ocular absorption into the aqueous humor
- B Conjunctival absorption into choroidal vessels
- C Nasolacrimal drainage with systemic absorption via nasal mucosa bypassing first-pass metabolism ✓
- D Corneal endothelial transfer to systemic circulation
Correct answer: C. Nasolacrimal drainage with systemic absorption via nasal mucosa bypassing first-pass metabolism
Explanation
Topical eye drops drain via the nasolacrimal duct into the nasal mucosa, where they are absorbed directly into systemic circulation without hepatic first-pass metabolism. This results in higher effective systemic concentrations compared to oral absorption. Timolol, a non-selective beta-blocker, can cause bronchoconstriction, bradycardia, and heart block. Nasolacrimal occlusion (punctal occlusion) after instillation significantly reduces systemic absorption. Conjunctival and corneal routes contribute minimally.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.