Chirality and drug withdrawals<\/strong><\/p>\n\n\n\n Labetalol has two stereogenic centers and consequently exists as four stereoisomers. It is a diastereoisomeric mixture of approximately equal amounts of all four possible stereoisomers ((R,S)-labetalol, (S,R)-labetalol, (S,S)-labetalol and (R,R)-labetalol). The (S<\/em>,S<\/em>)- and (R<\/em>,S<\/em>)- forms are inactive. The third, the (S<\/em>,R<\/em>)-isomer, is a powerful \u03b11<\/sub>-blocker. The fourth isomer, the (R<\/em>,R<\/em>)-isomer is Dilevalol.<\/p>\n\n\n\n Compared to the racemate, dilevalol has four times \u03b21-adrenorecptor blocking and seven-fold vasodilatory activity due to its agonist activity at the \u03b22-adrernorecpors. Clinically, introduction of dilevalol generated big enthusiasm as it represented a new generation of \u03b2-blockers with vasodilating activity. Soon after its introduction in the market in 1989, reports of hepatotoxicity began to appear. Although labetalol is known to manifest hepatotoxicity, the rate of incidence appeared to be lower than that associated with dilevalol. Hence dilevalol was withdrawn from market in 1990.<\/p>\n\n\n\n Nomenclature<\/strong><\/p>\n\n\n\n (R,R)-labetalol is a 2-hydroxy-5-{1-hydroxy-2-[(4-phenylbutan-2-yl)amino]ethyl} benzamide that has 1R,2R-configuration. 2-Hydroxy-5-((R)-1-hydroxy-2-(((R)-4-phenylbutan-2-yl)amino)ethyl)benzamide<\/p>\n\n\n\n Therapeutic category<\/strong><\/p>\n\n\n\n Withdrawn from market in 1990<\/strong> due to stereochemically engineered toxicity<\/strong><\/p>\n\n\n\n Exercise<\/strong><\/p>\n\n\n\n Understand the stereo-descriptors employed in the nomenclature<\/p>\n\n\n\n Study the stereoisomeric relationship between all the four stereoisomer of labetalol<\/p>\n\n\n\n References<\/strong><\/p>\n\n\n\n https:\/\/pubchem.ncbi.nlm.nih.gov\/compound\/Dilevalol<\/a><\/p>\n\n\n\n Eichelbaum, Michel F., Testa, Bernard, Somogyi, Andrew (Eds.). Stereochemical aspects of drug action and disposition, Springer, Page 401-32, 2003.<\/p>\n\n\n\n![\"\"](\"https:\/\/chiralpedia.com\/blog\/wp-content\/uploads\/2022\/08\/Labetalol-steroisomers-3.png\")
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