A patient with primary open-angle glaucoma unresponsive to timolol is started on echothiophate eye drops. Before elective surgery, the anaesthetist must be warned about a specific interaction. Which perioperative hazard is characteristic of chronic echothiophate use?
- A Prolonged apnoea after succinylcholine administration ✓
- B Marked resistance to non-depolarising muscle relaxants
- C Severe hypertension after indirect sympathomimetics
- D Reduced efficacy of neostigmine reversal
Correct answer: A. Prolonged apnoea after succinylcholine administration
Explanation
Echothiophate is an irreversible organophosphate cholinesterase inhibitor used as a long-acting miotic. Systemically absorbed enzyme inhibition slows succinylcholine hydrolysis by plasma pseudocholinesterase, so standard doses produce markedly prolonged paralysis and apnoea that may last hours. Non-depolarising relaxants would be potentiated, not resisted, and neostigmine remains effective since it competes at the enzyme active site. Indirect sympathomimetics are unaffected by pseudocholinesterase inhibition.
Reference: Katzung's Basic and Clinical Pharmacology, 15th ed.
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