A 24 years old farm worker is rushed to, a nearby emergency department after an accidental exposure to parathion. Which of the following drugs can be given to increase the activity of his acetyl cholinesterase:
## Core Concept
The core concept here involves understanding the mechanism of action of organophosphate poisoning, specifically parathion, and the treatment strategies for such poisoning. Parathion is an organophosphate compound that acts as an irreversible inhibitor of **acetylcholinesterase (AChE)**, the enzyme responsible for breaking down **acetylcholine (ACh)** into choline and acetic acid. Inhibition of AChE leads to an accumulation of ACh in the synaptic cleft, causing overstimulation of acetylcholine receptors.
## Why the Correct Answer is Right
The correct answer, **pralidoxime (2-PAM)**, works by reactivating acetylcholinesterase that has been phosphorylated by organophosphate compounds like parathion. Pralidoxime acts as a nucleophile, directly reactivating the inhibited enzyme by removing the phosphate group. This process restores the normal function of acetylcholinesterase, allowing it to hydrolyze acetylcholine again. Pralidoxime is most effective when given soon after exposure, as it cannot reactivate acetylcholinesterase that has undergone **aging**, a process that occurs over time and makes the enzyme resistant to reactivation.
## Why Each Wrong Option is Incorrect
- **Option A:** Atropine is used in the management of organophosphate poisoning but works by blocking muscarinic acetylcholine receptors, not by reactivating acetylcholinesterase. It helps manage symptoms like bradycardia, bronchial secretions, and sweating but does not restore enzyme activity.
- **Option B:** This option seems to be a placeholder and does not provide a recognizable drug related to the treatment of organophosphate poisoning or the activation of acetylcholinesterase.
- **Option D:** This option also appears to be a placeholder and does not correspond to a known treatment for enhancing acetylcholinesterase activity in the context of organophosphate poisoning.
## Clinical Pearl / High-Yield Fact
A critical point to remember is that the effectiveness of pralidoxime decreases over time due to the **aging** process of the phosphorylated acetylcholinesterase. Therefore, early administration of pralidoxime is crucial for optimal benefit. Additionally, pralidoxime does not cross the blood-brain barrier effectively, so it does not treat the central nervous system effects of organophosphate poisoning.
## Correct Answer Line
**Correct Answer: C. Pralidoxime**.