SPL Set ID: f8bb3427-c887-47b6-8042-8a21dc161c79

Midazolam hydrochloride is a water-soluble benzodiazepine available as a sterile, nonpyrogenic parenteral dosage form for intravenous or intramuscular injection. Each mL contains midazolam hydrochloride equivalent to 1 mg or 5 mg midazolam in sterile water for injection. In addition, each mL contains the following inactive ingredients: 0.8% sodium chloride and 0.01% edetate disodium, with 1% benzyl alcohol as preservative; the pH is adjusted to 2.5-3.7 with sodium hydroxide and, if necessary, hydrochloric acid. Midazolam is a white to light yellow crystalline compound, insoluble in water. The hydrochloride salt of midazolam, which is formed in situ , is soluble in aqueous solutions. Chemically, midazolam HCl is 8-chloro-6-(2-fluorophenyl)-1-methyl-4 H -imidazo[1,5-a][1,4]benzodiazepine hydrochloride. Midazolam hydrochloride has the molecular formula C 18 H 13 ClFN 3 • HCl, a calculated molecular weight of 362.25 and the following structural formula: Under the acidic conditions required to solubilize midazolam in the product, midazolam is present as an equilibrium mixture (shown below) of the closed-ring form and an open-ring structure formed by the acid-catalyzed ring opening of the 4,5-double bond of the diazepine ring. The amount of open-ring form is dependent upon the pH of the solution. At the specified pH of the product, the solution may contain up to about 25% of the open-ring compound. At the physiologic conditions under which the product is absorbed (pH of 5 to 8) into the systemic circulation, any open-ring form present reverts to the physiologically active, lipophilic, closed-ring form (midazolam) and is absorbed as such. The following chart plots the percentage of midazolam present as the open-ring form as a function of pH in aqueous solutions. As indicated in the graph, the amount of open-ring compound present in solution is sensitive to changes in pH over the pH range specified for the product: 2.5 to 3.7. Above pH 5, at least 99% of the mixture is present in the closed-ring form. Structural Formula Image of Midazolam Present as an Equilibirum Mixture of Closed-Ring and Open-Ring Form Image of Chart Plotting the Percentage of Midazolam Present as the Open-Ring Form as a Function of pH in Aqueous Solutions