Doxapram hydrochloride monohydrate

Description

Doxapram is a central respiratory stimulant. It increases respiration and phrenic nerve activity in anesthetized cats at a dose of 1.0 mg/kg. Doxapram acts through carotid chemoreceptors, lacking activity in anesthetized cats following carotid denervation. Formulations containing doxapram have been used to increase respiration in patients with chronic pulmonary disease, respiratory depression induced by drug overdose, and to stimulate deep breathing post-anesthesia.

Chemical properties

White or almost white, crystalline powder.

Originator

Dopram,Robins,US,1965

The Uses of Doxapram hydrochloride monohydrate

antibacterial

Definition

ChEBI: The monohydrate form of doxapram hydrochloride. A central and respiratory stimulant with a brief duration of action, it is used as a temporary treatment of acute respiratory failure, particularly when superimposed on chronic obstructive pulmonary disease, nd of postoperative respiratory depression. It has also been used for treatment of postoperative shivering.

Manufacturing Process

(A) Preparation of α-(1-ethyl-3-pyrrolidyl)-α,α-diphenylacetonitrile: A suspension of the sodium salt of diphenylacetonitrile was formed by the dropwise addition at 50°C of 193 grams (1.0 mol) of diphenylacetonitrile to a stirred suspension of 43 grams (1.1 mols) of sodium amide in 1 liter of dry toluene. After addition was complete, the mixture was refluxed for 4 hours and then, to the refluxing mixture, 1.0 mol of 1-ethyl-3-chloropyrrolidine was added at a rapid dropwise rate with continuous stirring. After addition was complete, stirring and refluxing were continued for 3 hours. The mixture was then cooled and extracted with one normal hydrochloric acid. The aqueous layer together with an oil layer were separated, made basic with dilute sodium hydroxide, and extracted with ether. The ethereal solution was dried over sodium sulfate and concentrated and the residue was distilled in vacuo. The material crystallized from a 4:1 ethanol-water mixture.
(B) Preparation of 4-(β-chloroethyl)-3,3-diphenyl-1-ethyl-2-pyrrolidinone: A solution of α,α-diphenyl-α-(1-ethyl-3-pyrrolidyl)-acetonitrile in 70% sulfuric acid was heated at 130-140°C for 48 hours, poured onto ice, made basic with sodium hydroxide, and extracted with chloroform. The chloroform solution was acidified with hydrogen chloride gas, dried over sodium sulfate and concentrated. The residue was refluxed in 500 ml of thionyl chloride for 3 hours; the resulting solution was concentrated in vacuo; and the residue wascrystallized from isopropyl ether.
(C) Preparation of doxapram hydrochloride [3,3-diphenyl-1-ethyl-4-(2- morpholino-ethyl)-2-pyrrolidinone hydrochloride monohydrate]: A solution of 25 grams (0.076 mol) of 4-(2-chloroethyl)-3,3-diphenyl-1-ethyl-2- pyrrolidinone and 13.3 grams (0.153 mol) of morpholine in 500 ml of absolute ethanol was heated at 95°-120°C for 21 hours in a closed system and concentrated in vacuo. The residue was dissolved in 300 ml of two normal hydrochloric acid and extracted with 150 ml of ethyl acetate. A solid crystallized (13 g) during the extraction and was removed by filtration. MP 217°-219°C. The acid extracts were made basic with sodium hydroxide and extracted with ether, and the ether solution was concentrated in vacuo and the residue was suspended in six normal hydrochloric acid. Additional crystalline product formed and was recrystallized from two normal hydrochloric acid. Yield, 10 grams; MP 217°-219°C. Total yield, 23 grams (70%).

brand name

Dopram (Baxter Healthcare).

Therapeutic Function

Respiratory stimulant

General Description

Doxapram, 1-ethyl-4-(2-morpholinoethyl)-3,3-diphenyl-2-pyrrolidinone hydrochloride hydrate (Dopram), has an obscuremolecular mechanism of action. Overall, it stimulatesrespiration by action on peripheral carotid chemoreceptors.It has use as a respiratory stimulant postanesthetically, afterCNS depressant drug overdose, in chronic obstructive pulmonarydiseases, and in the apneas. Dopram is administeredexclusively by intravenous injection. Because of the benzylalcohol content of the injectable formulation, Dopram mustnever be given to neonates.

Clinical Use

Postoperative respiratory depression
Acute respiratory failure

Drug interactions

Potentially hazardous interactions with other drugs
Anaesthetics: increased risk of arrhythmias with volatile liquid general anaesthetics - avoid for at least 10 minutes after volatile liquid general anaesthetics.

Metabolism

Doxapram is extensively metabolised in the liver, and the major route of excretion of metabolites and a small amount of unchanged drug is thought to be via bile to the faeces.