A note on suxamethonium sensitivity and serum cholinesterase variants

Abstract
Sera from 21 cases of prolonged apnoea which showed normal phenotype (UU) on the basis of dibucaine and fluoride inhibition were re-examined by replacing the substrate benzoylcholine with succinylcholine (suxamethonium). 9 samples had normal enzyme activity but low dibucaine number (DN=<20) indicating the atypical variant; 6 sera showed no detectable enzyme activity. The remaining 6 samples had enzyme activity and DN comparable with healthy controls. The occurence of new variants of serum cholinesterase sensitive only to succinylcholine is suggested.