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Midazolam Hydrochloride Syrup

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Midazolam Hydrochloride Syrup

Midazolam Hydrochloride Syrup
(generic formulation)

Midazolam HCI syrup has been associated with respiratory depression and respiratory arrest, especially when used for sedation in noncritical care settings. Midazolam HCI syrup has been associated with reports of respiratory depression, airway obstruction, desaturation, hypoxia, and apnea, most often when used concomitantly with other central nervous system depressants (eg, opioids). Midazolam HCI syrup should be used only in hospital or ambulatory care settings, including physicians' and dentists' offices, THAT CAN PROVIDE FOR CONTINUOUS MONITORING OF RESPIRATORY AND CARDIAC FUNCTION. IMMEDIATE AVAILABILITY OF RESUSCITATIVE DRUGS AND AGE-AND SIZE- APPROPRIATE EQUIPMENT FOR VENTILATION AND INTUBATION, AND PERSONNEL TRAINED IN THEIR USE AND SKILLED IN AIRWAY MANAGEMENT SHOULD BE ASSURED (see WARNINGS). For deeply sedated patients, a dedicated individual, other than the practitioner performing the procedure, should monitor the patient throughout the procedure.


Midazolam is a benzodiazepine available as midazolam HCI syrup for oral administration. Midazolam, a white to light yellow crystalline compound, is insoluble in water, but can be solubilized in aqueous solutions by formation of the hydrochloride salt in situ under acidic conditions. Chemically, midazolam HCI is 8-chloro-6-(2-fluo-rophenyl)-1-methyl-4H-imidazo[1,5-a][1,4] benzodiazepine hydrochloride.Midazolam hydrochloride has the molecular formula C18H13CIFN3•HCI, a calculated molecular weight of 362.25 and the following structural formula:

MIDAZOLAM HYDROCHLORIDE  Structural Formula Illustration

Each mL of the syrup contains midazolam hydrochloride equivalent to 2 mg midazolam compounded with artificial bitterness modifier, citric acid anhydrous, D&C Red #33, edetate disodium, glycerin, mixed fruit flavor, sodium benzoate, sodium citrate, sorbitol, and water; the pH is adjusted to 2.8 - 3.6 with hydrochloric acid.

Under the acidic conditions required to solubilize midazolam in the syrup, midazolam is present as an equilibrium mixture (shown below) of the closed ring form shown above 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 syrup, the solution may contain up to about 40% 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.

MIDAZOLAM HYDROCHLORIDE  Structural Formula Illustration


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: 2.8 to 3.6.Above pH 5, at least 99% of the mixture is present in the closed-ring form.

pH Dependence of Open-ring Form in Water

MIDAZOLAM HYDROCHLORIDE pH Dependence of Open-ring Form in Water Illustration

Last reviewed on RxList: 6/25/2008
This monograph has been modified to include the generic and brand name in many instances.

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