In acute organophosphate poisoning, pralidoxime (PAM) is ineffective if administered after a certain critical window because the OP-AChE bond undergoes a process rendering it irreversible. What is this process called?
- A Hydrolysis
- B Aging ✓
- C Oxidative phosphorylation
- D Carbamoylation
Correct answer: B. Aging
Explanation
"Aging" refers to the time-dependent dealkylation of the phosphorylated AChE complex, resulting in an extremely stable, irreversible bond that PAM cannot break. The aging time varies by compound: soman ages within minutes, while parathion ages over hours to days. Once aging occurs, only synthesis of new AChE restores activity. Hydrolysis is spontaneous reactivation that occurs with less toxic OP compounds. Carbamoylation describes reversible inhibition by carbamates such as physostigmine.
Reference: The Essentials of Forensic Medicine and Toxicology (Narayan Reddy), 34th ed.
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