Dibucaine is a local anesthetic of the amide type now generally used for surface anesthesia. Dibucaine reversibly binds to and inactivates sodium channels in the neuronal cell membrane. Inhibition of sodium channels prevents the depolarization of nerve cell membranes and inhibits subsequent propagation of impulses along the course of the nerve, thereby limiting the excitation of nerve endings. This results in loss of sensation. Dibucaine inhibits normal butyrylcholinesterase activity. The percentage of butyrylcholine that remains unchanged in the blood of individuals administered a standard dose of dibucaine was the dibucaine number. This number was used to differentiate the genetic variants. A dibucaine number of 80 and above for wild type homozygotes (normal), 40-60 for heterozygotes (atypical), and 20 or less for atypical homozygotes (D70G)
Search PubMed for references concerning: Dibucaine
7 moreTitle: Genetic variants of human serum cholinesterase influence metabolism of the muscle relaxant succinylcholine. Lockridge O Ref: Pharmacol Ther, 47:35, 1990 : PubMed
People with genetic variants of cholinesterase respond abnormally to succinylcholine, experiencing substantial prolongation of muscle paralysis with apnea rather than the usual 2-6 min. The structure of usual cholinesterase has been determined including the complete amino acid and nucleotide sequence. This has allowed identification of altered amino acids and nucleotides. The variant most frequently found in patients who respond abnormally to succinylcholine is atypical cholinesterase, which occurs in homozygous form in 1 out of 3500 Caucasians. Atypical cholinesterase has a single substitution at nucleotide 209 which changes aspartic acid 70 to glycine. This suggests that Asp 70 is part of the anionic site, and that the absence of this negatively charged amino acid explains the reduced affinity of atypical cholinesterase for positively charged substrates and inhibitors. The clinical consequence of reduced affinity for succinylcholine is that none of the succinylcholine is hydrolyzed in blood and a large overdose reaches the nerve-muscle junction where it causes prolonged muscle paralysis. Silent cholinesterase has a frame shift mutation at glycine 117 which prematurely terminates protein synthesis and yields no active enzyme. The K variant, named in honor of W. Kalow, has threonine in place of alanine 539. The K variant is associated with 33% lower activity. All variants arise from a single locus as there is only one gene for human cholinesterase (EC 3.1.1.8). Comparison of amino acid sequences of esterases and proteases shows that cholinesterase belongs to a new family of serine esterases which is different from the serine proteases.
        
Title: Differential inhibition of plasma cholinesterase variants using the dibutyrate analogue of pancuronium bromide Whittaker M, Britten JJ Ref: Hum Hered, 31:242, 1981 : PubMed
A steroid, the dibutyrate analogue of pancuronium bromide (9.8 X 10(-8)M), has been used as differential inhibitor in the study of the plasma cholinesterase variants. Pancuronium dibutyrate numbers have been measured for 190 individuals, and the mean values for six of the known genotypes, E1uE1u, E1uE1f, E1uE1a, E1fE1a, E1aE1a, and E1fE1f, have been calculated. Evidence is presented that a combination of the pancuronium dibutyrate number and the fluoride number give better resolution of the six genotypes than the combination of the pancuronium dibutyrate and the dibucaine number. This new differential inhibitor has real potential for revealing the probable existence of new genotypes.
        
Title: The activity of various esterase inhibitors towards atypical human serum cholinesterase Kalow W, Davies R0 Ref: Biochemical Pharmacology, 1:183, 1958 : PubMed
7 lessTitle: Butyrylcholinesterase genes in individuals with abnormal inhibition numbers and with trace activity: one common mutation and two novel silent genes Dey DC, Maekawa M, Sudo K, Kanno T Ref: Annals of Clinical Biochemistry, 35:302, 1998 : PubMed
A random population was screened for abnormal dibucaine and fluoride numbers (DN & FN) to find some common mutations in butyrylcholinesterase (BCHE) gene. Of 2375 unrelated individuals, 10 were found to have low DN and FN and were selected for further studies. DNA analysis of these hypocholinesterasemics revealed that seven patients were heterozygous for missense mutation at codon 330 (TTA to ATA; BCHE*330I). The frequency of BCHE*330I mutation was calculated to be at least 0.29% among the Japanese. On the other hand, two novel mutations were found in three families and two individuals including probands whose enzyme activity was very low (silent gene). Polymerase chain reaction and single stranded conformation polymorphism (PCR-SSCP) and restriction fragment length polymorphism (PCR-RFLP) were used for identification of the common and known mutation types such as BCHE*250P (ACT to CCT), BCHE*365R (GGA to CGA), and BCHE*539T (GCA to ACA; K-polymorphism), whereas PCR-SSCP was used in combination with direct DNA sequencing for new mutations like BCHE*446V (TTT to GTT) and BCHE*451X (GAA to TAA).
Butyrylcholinesterase [BCHE (acylcholine acyl hydrolase); EC 3.1.1.8] limits the access of drugs, including tacrine, to other proteins. The "atypical" BCHE variant, in which Asp70 at the rim of the active site gorge is substituted by glycine, displayed a more drastically weakened interaction with tacrine than with cocaine, dibucaine, succinylcholine, BW284c51 [1,5-bis(4-allyldimethylammoniumphenyl)pentan-3-one dibromide], or alpha-solanine. To delineate the protein domains that are responsible for this phenomenon, we mutated residues within the rim of the active site gorge, the region parallel to the peripheral site in the homologous enzyme acetylcholinesterase [AChE (acetylcholine acetyl hydrolase); EC 3.1.1.7], the oxyanion hole, and the choline-binding site. When expressed in microinjected Xenopus laevis oocytes, all mutant DNAs yielded comparable amounts of immunoreactive protein products. Most mutants retained catalytic activity close to that of wild-type BCHE and were capable of binding ligands. However, certain modifications in and around the oxyanion hole caused a dramatic loss in activity. The affinities for tacrine were reduced more dramatically than for all other ligands, including cocaine, in both oxyanion hole and choline-binding site mutants. Modified ligand affinities further demonstrated a peripheral site in residues homologous with those of AChE. BCHE mutations that prevented tacrine interactions also hampered its ability to bind other drugs and inhibitors, which suggests a partial overlap of the binding sites. This predicts that in addition to their genetic predisposition to adverse responses to tacrine, homozygous carriers of "atypical" BCHE will be overly sensitive to additional anticholinesterases and especially so when exposed to several anticholinesterases in combination.
        
Title: Identification of human plasma cholinesterase variants in 6,688 individuals using biochemical analysis Jensen FS, Skovgaard LT, Viby-Mogensen J Ref: Acta Anaesthesiologica Scandinavica, 39:157, 1995 : PubMed
In 1973, a Cholinesterase Research Unit was established in Denmark (DCRU). The primary aim was to provide a central service for determining genotypes and activity of plasma cholinesterase (BChE) in patients showing abnormal response after succinylcholine. The purpose of the present study was, on the basis of 20 years experience with this Unit, to establish accurate reference intervals for BChE activity and inhibition values for the different genotypes of BChE. Also we wanted to evaluate the influence of age and sex on the BChE activity in genotypically normal patients. Plasma cholinesterase activity was measured using benzoylcholine as substrate. The genetic variations of the enzyme were identified using differential inhibitors, i.e.: Dibucaine, Sodium Fluoride, Succinylcholine, Urea and Ro-2-0683. We investigated 6,688 patients. The reference values for the 13 genotypes represented agree with previous findings. In genotypically normal patients, no age or sex differences were found in BChE activity in children below the age of 10 years. From the age of 10 years the activity decreased significantly in both males and females, the activity in females being significantly lower than in males. In females the activity was lowest in the age group 30-40 years, returning to prepuberty level at about 60 years of age. In males the activity decreased slightly up to 50-60 years of age. Hereafter the activity was stable or tended to increase slightly. Most genotypes could be recognized using the results of the different inhibition studies. We found the inhibitors Dibucaine, Sodium fluoride, Urea and Ro-2-0683 most helpful, whereas succinylcholine was of less value.
        
Title: [Prolonged neuromuscular block caused by succinylcholine in a patient with normal cholinesterase activity]. [Italian] Tritapepe L, Giardini M Ref: Minerva Anestesiol, 61:47, 1995 : PubMed
The authors describe a case of prolonged neuromuscular blockade following suxamethonlum in a patient with a normal cholinesterase activity and dibucaine number > or = 75%. In this case a peripheral nerve stimulator and capnography allowed neuromuscular blockade evaluation and fresh frozen plasma infusion led to a normal recovery from suxamethonium neuromuscular blockade. This report suggests a case of abnormal cholinesterase activity described as "silent variant".
        
Title: Plasma cholinesterase: gene and variations Pantuck EJ Ref: Anesthesia & Analgesia, 77:380, 1993 : PubMed
The traditional tests that have been used for the past 30 yr to determine plasma cholinesterase phenotype--measurement of esterase activity with a variety of substrates, dibucaine inhibition, fluoride inhibition, and Ro2-0683 inhibition--are inadequate for identifying some variants of this enzyme and leave many cases of prolonged response to succinylcholine unexplained. The application of the techniques of molecular genetics has permitted precise identification of plasma cholinesterase variants and has resulted in the discovery of previously unrecognized variants. It is now possible, in cases of prolonged response to succinylcholine resulting from genetically determined alterations in plasma cholinesterase, to ascertain the nature of the mutations in the alleles, and from them to deduce the structural changes in the enzymes responsible for the impairment in drug metabolism.
        
Title: Genetic variants of human serum cholinesterase influence metabolism of the muscle relaxant succinylcholine. Lockridge O Ref: Pharmacol Ther, 47:35, 1990 : PubMed
People with genetic variants of cholinesterase respond abnormally to succinylcholine, experiencing substantial prolongation of muscle paralysis with apnea rather than the usual 2-6 min. The structure of usual cholinesterase has been determined including the complete amino acid and nucleotide sequence. This has allowed identification of altered amino acids and nucleotides. The variant most frequently found in patients who respond abnormally to succinylcholine is atypical cholinesterase, which occurs in homozygous form in 1 out of 3500 Caucasians. Atypical cholinesterase has a single substitution at nucleotide 209 which changes aspartic acid 70 to glycine. This suggests that Asp 70 is part of the anionic site, and that the absence of this negatively charged amino acid explains the reduced affinity of atypical cholinesterase for positively charged substrates and inhibitors. The clinical consequence of reduced affinity for succinylcholine is that none of the succinylcholine is hydrolyzed in blood and a large overdose reaches the nerve-muscle junction where it causes prolonged muscle paralysis. Silent cholinesterase has a frame shift mutation at glycine 117 which prematurely terminates protein synthesis and yields no active enzyme. The K variant, named in honor of W. Kalow, has threonine in place of alanine 539. The K variant is associated with 33% lower activity. All variants arise from a single locus as there is only one gene for human cholinesterase (EC 3.1.1.8). Comparison of amino acid sequences of esterases and proteases shows that cholinesterase belongs to a new family of serine esterases which is different from the serine proteases.
        
Title: Comparison of a commercially available assay system with two reference methods for the determination of plasma cholinesterase variants Whittaker M, Britten JJ, Dawson PJ Ref: Clinical Chemistry, 29:1746, 1983 : PubMed
For assaying plasma cholinesterase (EC 3.1.1.8) activity and phenotyping by means of dibucaine inhibition, we have compared a commercially available kit, in which butyrylthiocholine is used as substrate, with two reference methods, one using benzoylcholine and the other propionylthiocholine. With 50 different samples of three of the most common genetic variants, we could clearly differentiate the variants with benzoylcholine and dibucaine, whereas there was some overlap of the E1uE1u and E1uE1a phenotypes with the other two substrates at 30 degrees C. The phenotypes were better differentiated at 25 degrees C, and in our hands the use of butyrylthiocholine was preferable to propionylthiocholine for phenotyping with dibucaine. The affinity of the usual and atypical homozygotes for fluoride with butyrylthiocholine gave an inverted response to the affinity of these variants for the anion with benzoylcholine. We suggest that this may be explained by the role of the chromogen or its products in the assay procedure with the thiocholine substrate.
        
Title: Differential inhibition of plasma cholinesterase variants using the dibutyrate analogue of pancuronium bromide Whittaker M, Britten JJ Ref: Hum Hered, 31:242, 1981 : PubMed
A steroid, the dibutyrate analogue of pancuronium bromide (9.8 X 10(-8)M), has been used as differential inhibitor in the study of the plasma cholinesterase variants. Pancuronium dibutyrate numbers have been measured for 190 individuals, and the mean values for six of the known genotypes, E1uE1u, E1uE1f, E1uE1a, E1fE1a, E1aE1a, and E1fE1f, have been calculated. Evidence is presented that a combination of the pancuronium dibutyrate number and the fluoride number give better resolution of the six genotypes than the combination of the pancuronium dibutyrate and the dibucaine number. This new differential inhibitor has real potential for revealing the probable existence of new genotypes.
        
Title: [Inhibition of cholinesterase and acetylcholinesterase in rats by dibucaine] Schnurr E Ref: Arzneimittelforschung, 17:1577, 1967 : PubMed
Title: The activity of various esterase inhibitors towards atypical human serum cholinesterase Kalow W, Davies R0 Ref: Biochemical Pharmacology, 1:183, 1958 : PubMed