Midazolam maleate salt

Description

Midazolam maleate, 8- chloro-6-(2-fluorophenyl)?1-methyl-4Himidazo-benzodiazepine maleate , is a stable, water-soluble powder. The solubility in water depends on pH:≈85 mg/mL at pH 2.7 and 0.3 mg/mL at pH 7.6. The maleate is subject to reversible ring opening. Below pH4 the ring is open; above pH 4 the cyclic form is present. The anesthetic formulation is a buffered aqueous solution containing 2.5 mg/mL at pH 3.5.

Originator

Dormicum,Roche,Switz.,1982

The Uses of Midazolam maleate salt

Sedative; ligand GABA receptor benzodiazepine modulatory site

Manufacturing Process

Acetic anhydride (7 ml) was added to a solution of 6.16 g of crude 2- aminomethyl-7-chloro-2,3-dihydro-5-(2-fluorophenyl)-1H-1,4-benzodiazepine in 200 ml of methylene chloride. The solution was added to 200 ml of saturated aqueous sodium bicarbonate and the mixture was stirred for 20 minutes. The organic layer was separated, washed with sodium bicarbonate, dried over sodium sulfate and evaporated to leave resinous 2- acetylaminomethyl-7-chloro-2,3-dihydro-5-(2-fluorophenyl)-lH -l,4- benzodiazepine. This material was heated with 40 g of polyphosphoric acid at 150°C for 10 minutes. The cooled reaction mixture was dissolved in water, made alkaline with ammonia and ice and extracted with methylene chloride. The extracts were dried and evaporated and the residue was chromatographed over 120 g of silica gel using 20% methanol in methylene chloride. The clean fractions were combined and evaporated to yield resinous 8-chloro-3a,4-dihydro-6-(2-fluorophenyl)-1- methyl-4H-imidazo[1,5-a][1,4] - benzodiazepine.
A mixture of this material with 500 ml of toluene and 30 g of manganese dioxide was heated to reflux for 1? hours. The manganese dioxide was separated by filtration over Celite. The filtrate was evaporated and the residue was crystallized from ether to yield 8-chloro-6-(2-fluorophenyl)-1-methyl-4Himidazo[1,5-a][1,4]benzodiazepine, melting point 152°C to 154°C. The analytical sample was recrystallized from methylene chloride/hexane.
A warm solution of 6.5 g (0.02 mol) of 8-chloro-6-(2-fluorophenyl)-1-methyl- 4H-imidazo[1,5-a] [1,4]-benzodiazepine in 30 ml of ethanol was combined with a warm solution of 2.6 g (0.022 mol) of maleic acid in 20 ml of ethanol. The mixture was diluted with 150 ml of ether and heated on the steam bath for 3 minutes. After cooling, the crystals were collected, washed with ether and dried in vacuo to yield 8-chloro-6-(2-fluorophenyl)-1-methyl-4Himidazo[1.5-a] [1,4]-benzodiazepine maleate, melting point 148°C to 151°C.

Therapeutic Function

Anesthetic

Biochem/physiol Actions

Sedative/Hypnotic; ligand for the GABAA receptor benzodiazepine modulatory site; CYP3A4 substrate.

Synthesis

The preparation starts with 7-chloro- 5-(2-fluorophenyl)?1,3-dihydro-2H-1,4- benzodiaze-pinone . For the literature, also see . Midazolam is approximately twice as active as diazepam, causes less pain at the injection site, and has a shorter half-life than diazepam. Side effects: dose-dependent cerebral depression with tranquilization, sedation, and dryness. Reduction in blood pressure, respiratory depression, and cardiovascular effects were slight.