Droperidol is an antidopaminergic drug used as an antiemetic and antipsychotic. Droperidol is also often used for neuroleptanalgesic anesthesia and sedation in intensive-care treatment. Droperidol is synthesized from 1-benzyl-3-carbethoxypiperidin-4-one, which is reacted with o-phenylendiamine. Evidently, the first derivative that is formed under the reaction conditions, 1,5-benzdiazepine, rearranges into 1-(1-benzyl-1,2,3,6-tetrahydro-4-piridyl)-2-benzymidazolone. Debenzylation of the resulting product with hydrogen over a palladium catalyst, and subsequent alkylation of this using 4-chloro-4'-fluorobutyrophenone yields droperidol. Dysphoria, sedation, hypotension resulting from peripheral alpha adrenoceptor blockade, prolongation of QT interval which can lead to torsades de pointes, and extrapyramidal side effects such as dystonic reactions/neuroleptic malignant syndrome.
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