**Question:** Myasthenics are resistant to following muscle relaxant –

A. Valium (diazepam)
B. Baclofen
C. Suxamethonium
D. Pancuronium

**Core Concept:** Myasthenia gravis is a neuromuscular junction disorder characterized by autoimmune dysfunction, leading to reduced acetylcholine receptor binding and impaired neuromuscular transmission. Myasthenics, patients with myasthenia gravis, require muscle relaxants to counteract the disease's effects during surgery.

**Why the Correct Answer is Right:** Pancuronium is a non-depolarizing neuromuscular blocking agent that acts as a competitive antagonist to acetylcholine at the neuromuscular junction. In myasthenics, there is already reduced acetylcholine receptor binding due to the disease. Therefore, using a muscle relaxant like pancuronium would exacerbate the disease's effects and worsen the patient's muscle weakness, rendering it inappropriate.

**Why Each Wrong Option is Incorrect:**

A. Valium (diazepam) is a benzodiazepine that primarily acts as a GABA agonist and is not a muscle relaxant. It does not address the issue of reduced acetylcholine receptor binding in myasthenics.

B. Baclofen is a GABA agonist used primarily for spasticity management in neurological disorders, not neuromuscular blockage. It does not target the neuromuscular junction issue in myasthenics.

C. Suxamethonium is a short-acting, non-depolarizing muscle relaxant that acts by blocking the neuromuscular junction and depolarizing the muscle fibres. In myasthenics, this would exacerbate the disease's effects, making it unsuitable.

**Clinical Pearl:** In myasthenia gravis, muscle relaxants should be avoided or used with extreme caution, as they would worsen the disease's symptoms and potentially lead to severe respiratory muscle weakness, which can be life-threatening.

**Correct Answer:** C. Suxamethonium (it is a depolarizing muscle relaxant)

**Why Each Wrong Option is Incorrect:**

A. Valium (diazepam) is a benzodiazepine, which acts as a GABA agonist and is not a muscle relaxant. It does not address the issue of reduced acetylcholine receptor binding in myasthenics.

B. Baclofen is a GABA agonist used primarily for spasticity management in neurological disorders, not neuromuscular blockage. It does not target the neuromuscular junction issue in myasthenics.

C. Suxamethonium is a depolarizing muscle relaxant that acts by blocking the neuromuscular junction and depolarizing the muscle fibers. In myasthenia gravis, this would exacerbate the disease's symptoms and potentially lead to severe respiratory muscle weakness, which can be life-threatening.

D. Pancuronium is a depolarizing muscle relaxant that