Shortened action of succinylcholine in individuals with cholinesterase C5 isozyme

To test the possibility that individuals with and without plasma cholinesterase C5 isozyme have differences in neuromuscular sensitivity to succinylcholine chloride, we examined the effects of succinylcholine in these two groups of patients. Sera from 491 adult patients were examined for presence of the plasma cholinesterase C5 isozyme by use of electrophoresis with polyacrylamide; 24 were positive for the C5 isozyme. Plasma cholinesterase activity and duration of action of succinylcholine were measured in 12 C5 positive patients and 18 C5 negative patients, all of whom had the normal cholinesterase genotype. C5 positive patients had 30.1 per cent higher mean plasma cholinesterase activity than C5 negative patients. The duration of neuromuscular blockade, measured by the first twitch height evoked by train-of-four stimulation, was significantly shorter in C5 positive patients than C5 negative patients. The C5 positive individuals had shorter duration of action of succinylcholine than C5 negative individuals.