Question

A person was given a muscle relaxant that competitively blocks nicotinic receptors.

• A. Neostigmine
• B. Carbachol
• C. Succinylcholine
• D. Physostigmine

Answer 1

The Correct Option is A

To understand why Neostigmine is the correct answer, it's essential to grasp how different substances interact with nicotinic receptors:

1. Nicotinic receptors are a type of acetylcholine receptor found in muscle tissues, crucial for muscle contraction.

2. Competitive blockers inhibit the normal action of neurotransmitters like acetylcholine by binding to these receptors, preventing muscle contraction.

3. Neostigmine is an acetylcholinesterase inhibitor, which increases the concentration of acetylcholine at neuromuscular junctions by inhibiting its breakdown. This counteracts the effect of competitive blockers that block nicotinic receptors, helping in muscle relaxation recovery.

4. Carbachol and Succinylcholine directly stimulate nicotinic receptors rather than blocking them. They do not fit the profile of a competitive blocker.

5. Physostigmine is also an acetylcholinesterase inhibitor like neostigmine and primarily affects muscarinic receptors.

Therefore, considering these interactions, Neostigmine is the correct option as it increases acetylcholine levels to overcome competitive blocking of nicotinic receptors, facilitating the restoration of normal neuromuscular activity.