**Question:** In pseudocholinesterase deficiency, drug to be used cautiously is

A. Succinylcholine
B. Mivacurium
C. Vecuronium
D. Atracurium

**Correct Answer:** A. Succinylcholine

**Core Concept:**
Pseudocholinesterase deficiency is a rare genetic disorder where there is reduced activity of pseudocholinesterase enzyme in the blood. This enzyme plays a crucial role in the inactivation of succinylcholine, a muscle relaxant used for rapid-sequence induction of anaesthesia in surgeries.

**Why the Correct Answer is Right:**
Succinylcholine is a short-acting muscle relaxant that blocks neuromuscular transmission, leading to muscle relaxation and rapid intubation during surgery. In individuals with pseudocholinesterase deficiency, the enzyme responsible for breaking down succinylcholine is impaired, leading to prolonged duration of action and increased risk of complications, such as hyperkalemia and prolonged apnea.

**Why Each Wrong Option is Incorrect:**
B. Mivacurium: This is a long-acting neuromuscular blocking agent that does not require pseudocholinesterase for inactivation and is therefore less affected by pseudocholinesterase deficiency.
C. Vecuronium: This is another long-acting neuromuscular blocking agent that does not require pseudocholinesterase for inactivation and is less affected by pseudocholinesterase deficiency.
D. Atracurium: This is another long-acting neuromuscular blocking agent that does not require pseudocholinesterase for inactivation and is less affected by pseudocholinesterase deficiency.

**Clinical Pearl:**
In patients with pseudocholinesterase deficiency, the use of succinylcholine should be avoided or used with caution, as it can lead to complications. Other neuromuscular blocking agents, such as those mentioned above, do not require pseudocholinesterase for inactivation and are less affected by pseudocholinesterase deficiency. This ensures safer and more predictable muscle relaxation during surgery in such patients.

**Core Concept:**
Pseudocholinesterase deficiency is caused by mutations in the PON1 gene, which codes for pseudocholinesterase enzyme. The reduced activity of pseudocholinesterase leads to prolonged action of succinylcholine and increased risk of complications.

**Why Each Wrong Option is Incorrect:**
Mivacurium, vecuronium, and atracurium are long-acting muscle relaxants that require pseudocholinesterase for inactivation. These drugs are less affected by pseudocholinesterase deficiency, ensuring safer and more predictable muscle relaxation in this patient population.

**Clinical Pearl:**
When assessing patients for surgery, it is essential to verify pseudocholinesterase levels to determine the risk of succinylcholine use in patients with known or suspected pseudocholinesterase deficiency. In these patients, non-depolarizing muscle relaxants like mivacurium, vecuronium, and atracurium should be