All of the following statements about neuromuscular blockage produced by succinylcholine are true, except:
**Core Concept**
Succinylcholine is a depolarizing neuromuscular blocker that acts by binding to nicotinic acetylcholine receptors at the neuromuscular junction, causing prolonged depolarization and blockade. Unlike non-depolarizing agents, it produces a unique pattern of neuromuscular response, including rapid onset and lack of post-tetanic facilitation.
**Why the Correct Answer is Right**
Succinylcholine causes **no fade on tetanic stimulation** — this is a hallmark of depolarizing blockade. After a brief initial depolarization, the receptor becomes desensitized, and further stimulation fails to elicit a response. Thus, **fade on tetanic stimulation is false** and therefore the exception. The correct statement is that there is **no post-tetanic facilitation** (Option C), and **train of four ratio remains >0.4** (Option D), as the blockade is not reversible by stimulation. Option A is true because the response does not fade with train of four stimulation due to receptor desensitization.
**Why Each Wrong Option is Incorrect**
Option A: **Incorrect** — This statement is true; succinylcholine shows no fade on train of four stimulation due to receptor desensitization.
Option C: **Incorrect** — This statement is true; succinylcholine lacks post-tetanic facilitation because the receptor is permanently desensitized.
Option D: **Incorrect** — This statement is true; the train of four ratio remains high (>0.4) because the response is not suppressed by repetitive stimulation.
**Clinical Pearl / High-Yield Fact**
Succinylcholine causes **no post-tetanic facilitation** and **no fade on train of four stimulation** — key features that distinguish it from non-depolarizing neuromuscular blockers. Always remember: **"Fade = non-depolarizing; No fade = depolarizing"**.
✓ Correct Answer: B. Fade on tetanic stimulation