A prolonged neuromuscular block with succinylcholine is not seen in which scenario?

A prolonged neuromuscular block with succinylcholine is not seen in which scenario?

• A. Chronic malathion exposure
• B. Echothiophate for glaucoma
• C. Cyclophosphamide for metastatic cancer
• D. C5 isoenzyme variant

Answer: (D)

The duration of a succinylcholine block depends on how fast plasma cholinesterase (butyrylcholinesterase) breaks it down. If this enzyme is inhibited or deficient, the drug stays around longer at the neuromuscular junction and the blockade is prolonged. Chronic malathion exposure inhibits cholinesterase, so succinylcholine persists longer. Echothiophate for glaucoma also inhibits cholinesterase, leading to a longer block. Cyclophosphamide, while it can have many systemic effects, does not directly affect plasma cholinesterase activity to prolong the block. Among enzyme variants, most slow-hydrolyzing forms can prolong the effect, but the C5 isoenzyme variant is not associated with clinically prolonged succinylcholine effect. Therefore, the scenario that does not produce a prolonged block is the C5 isoenzyme variant.

The duration of a succinylcholine block depends on how fast plasma cholinesterase (butyrylcholinesterase) breaks it down. If this enzyme is inhibited or deficient, the drug stays around longer at the neuromuscular junction and the blockade is prolonged. Chronic malathion exposure inhibits cholinesterase, so succinylcholine persists longer. Echothiophate for glaucoma also inhibits cholinesterase, leading to a longer block. Cyclophosphamide, while it can have many systemic effects, does not directly affect plasma cholinesterase activity to prolong the block. Among enzyme variants, most slow-hydrolyzing forms can prolong the effect, but the C5 isoenzyme variant is not associated with clinically prolonged succinylcholine effect. Therefore, the scenario that does not produce a prolonged block is the C5 isoenzyme variant.