tailieunhanh - Drugs and Poisons in Humans - A Handbook of Practical Analysis (Part 40)

Introduction: Local anaesthetics reversibly block neural transmission in local tissues. The drugs are bound with specific receptors located inside the sodium channels of cell membranes, and thus block the permeability of sodium ions; this is the mechanism of anaesthetic action of these drugs. As the history of local anaesthetics, Von Anrep discovered the local anaesthetic action of an alkaloid cocaine being contained in the leaves of Erythroxylon coca. Then, Karl Koller used cocaine as a local anaesthetic in ophthalmological surgery. Since the middle of 1980s, an explosive abuse of cocaine appeared, because of its strong addictive effects on the central. | Local a naesthetics by Fumio Moriya Introduction Local anaesthetics reversibly block neural transmission in local tissues. The drugs are bound with specific receptors located inside the sodium channels of cell membranes and thus block the permeability of sodium ions this is the mechanism of anaesthetic action of these drugs. As the history of local anaesthetics Von Anrep discovered the local anaesthetic action of an alkaloid cocaine being contained in the leaves of Erythroxylon coca. Then Karl Koller used cocaine as a local anaesthetic in ophthalmological surgery. Since the middle of 1980s an explosive abuse of cocaine appeared because of its strong addictive effects on the central nervous system overwhelming the local effects causing a serious social problem internationally. In place of cocaine procaine appeared in 1905 as the first synthetic local anaesthetic followed by the appearance of many synthetic drugs until nowadays. Local anaesthetics can be classified into ester-type and amide-type drugs according to their structures. Both types of the drugs differ in the mode of metabolism and chemical stability. The ester-type local anaesthetics are easily hydrolyzed by the action of pseudocholinesterase in blood plasma and are also rapidly decomposed in alkaline solutions nonenzymatically. Amide-type drugs are mainly metabolized by the liver microsomes and relatively stable in alkaline solutions. Structures physicochemical properties and clinical applications for cocaine and other local anaesthetics being frequently used in Japan are summarized in Table . According to the literature 1 published by National Research Institute of Police Science Japan seven fatal poisoning cases due to local anaesthetics were reported to have occurred in 1995-1999. The contents of the cases were 4 cases of suicide by oral and intravenous administration of lidocaine one case each of medical accidents due to lidocaine mepivacaine and dibucaine. The local anaesthetics show .