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Pseudocholinesterase (or plasma cholinesterase) is produced in the liver and metabolizes succinylcholine, ester local anesthetics, and mivacurium. Inherited forms of pseudocholinesterase deficiency occur as a result of mutations on the long arm of chromosome 3. Dibucaine is an amide local anesthetic that inhibits normal plasma cholinesterase by 80% and the atypical enzyme by 20%. The dibucaine number characterizes the ability to metabolize succinylcholine but does not reflect the quantity of enzyme. Normal homozygote has dibucaine number 80 with normal response to succinylcholine. Atypical heterozygote has dibucaine number 50-60 with prolonged duration of action for succinylcholine of 50-100%. Atypical homozygote has dibucaine number 20 with prolonged neuromuscular blockade with succinylcholine of 4-8 hours.