Pregnancy
category C (US) Metabolism CAS ID 548-73-2 | ATC code N05AD08 (WHO) Biological half-life 2.3 hours Molar mass 379.428 g/mol | |
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Routes of
administration Intravenous, Intramuscular Legal status UK: POM (Prescription only)
US: ℞-only | ||
Droperidol
Droperidol /droʊˈpɛrIdɔːl/ (Inapsine, Droleptan, Dridol, Xomolix, Innovar [combination with fentanyl]) is an antidopaminergic drug used as an antiemetic and antipsychotic. Droperidol is also often used for neuroleptanalgesic anesthesia and sedation in intensive-care treatment.
Contents
What does droperidol mean
History and use
Discovered at Janssen Pharmaceutica in 1961, droperidol is a butyrophenone, and is a potent D2 (dopamine receptor) antagonist with some histamine and serotonin antagonist activity. It has a central antiemetic action and effectively prevents postoperative nausea and vomiting in adults using doses as low as 0.625 mg. It has also been used as an antipsychotic in doses ranging from 5 to 10 mg given as an intramuscular injection, generally in cases of severe agitation in a psychotic patient who is refusing oral medication. Its use in intramuscular sedation has been replaced by intramuscular preparations of haloperidol, midazolam, clonazepam and olanzapine. Some practitioners recommend the use of 0.5 mg to 1 mg intravenously for the treatment of vertigo in an otherwise healthy elderly patients who have not responded to Epley maneuvers.
Black box warning
In 2001, the FDA changed the labeling requirements for droperidol injection to include a Black Box Warning, citing concerns of QT prolongation and torsades de pointes. The evidence for this is disputed, with 9 reported cases of torsades in 30 years and all of those having received doses in excess of 5 mg. QT prolongation is a dose-related effect, and it appears that droperidol is not a significant risk in low doses.
Side effects
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.
Chemistry
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.
(See pimozide article for proposed mechanism of intramolecular rearrangement.)