A 3-year-old child is treated with topical 1% atropine for amblyopia penalisation. The mother reports flushing, fever, and tachycardia 30 minutes after instillation. The mechanism of this systemic toxicity and its prevention is best explained by:

• A Trans-corneal absorption causing systemic cholinergic stimulation; prevented by using pilocarpine
• B Conjunctival venous absorption causing direct cardiac sensitisation; prevented by reducing drop volume
• C Eyelid skin absorption causing anticholinergic crisis; prevented by ophthalmological ointment instead
• D Nasolacrimal drainage delivering atropine to nasal mucosa for systemic absorption; prevented by nasolacrimal occlusion after instillation ✓

Explanation

The primary route of systemic absorption of topical ophthalmic medications is via the nasolacrimal duct — tears drain into the nasopharyngeal mucosa where the drug is rapidly absorbed into systemic circulation, bypassing first-pass metabolism. In children, atropine systemic toxicity (anticholinergic syndrome: tachycardia, flushing, pyrexia, dry skin) is a real risk. Nasolacrimal occlusion (punctal occlusion or gentle eyelid closure for 1–2 minutes) is the evidence-based preventive measure. Atropine itself causes anticholinergic, not cholinergic, effects.

Reference: Khurana Comprehensive Ophthalmology, 7th ed.

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Written and medically reviewed by the StethoPrep medical team.