**Question:** Suxamethonium causes -

A. Depolarization
B. Repetitive Tetanic Fibrillation
C. Post-tetanic Fatigue
D. Spinal Muscular Atrophy

**Core Concept:**
Suxamethonium is a non-depolarizing neuromuscular blocking agent used for rapid-sequence induction of general anesthesia. It acts on nicotinic acetylcholine receptors at the neuromuscular junction, blocking the transmission of nerve impulses to skeletal muscles.

**Why the Correct Answer is Right:**
Suxamethonium causes **Repetitive Tetanic Fibrillation** because it selectively blocks the acetylcholine receptors at the neuromuscular junction, preventing the release of acetylcholine and thereby inhibiting muscle contraction. This rapid blockade results in a brief period of muscle relaxation suitable for intubation and surgical procedures.

**Why Each Wrong Option is Incorrect:**
A. **Depolarization**: Suxamethonium does not cause depolarization directly, but it does interfere with the neuromuscular transmission process.

B. **Repetitive Tetanic Fibrillation**: This option is incorrect because suxamethonium results in a brief period of muscle relaxation due to its rapid onset of action.

C. **Post-tetanic Fatigue**: This option is incorrect because suxamethonium causes a rapid blockage of neuromuscular transmission, which does not lead to post-tetanic fatigue.

D. **Spinal Muscular Atrophy**: This option is irrelevant to the question as it describes a genetic disorder affecting skeletal muscles, not the effect of a neuromuscular blocking agent like suxamethonium.

**Clinical Pearl:**
Understanding the mechanism of action and clinical implications of neuromuscular blocking agents like suxamethonium is crucial for safe and effective anesthetic practice, particularly in rapid-sequence intubation and emergency situations. It is essential to recognize the appropriate use and limitations of these medications while considering potential complications like myasthenia gravis patients, which may be unresponsive to neuromuscular blocking agents due to impaired receptor function.