Source of information: Drugbank (External Link). Last updated on: 3rd July 18
*Trade Name used in the content below may not be the same as the HSA-registered product.
Active Ingredient / Synonyms
Buccolam | Dormicum | Midazolam | Midazolamum | Midazolam |
A short-acting hypnotic-sedative drug with anxiolytic and amnestic properties. It is used in dentistry, cardiac surgery, endoscopic procedures, as preanesthetic medication, and as an adjunct to local anesthesia. The short duration and cardiorespiratory stability makes it useful in poor-risk, elderly, and cardiac patients. It is water-soluble at pH less than 4 and lipid-soluble at physiological pH. [PubChem] Midazolam is a schedule IV drug in the United States.
The midazolam injection is indicated for preoperative sedation/anziolysis/amnesia. It is also an agent for sedation/anziolysis/amnesia prior to or during diagnostic, therapeutic, or endoscopic procedures. Midazolam can also be given intravenously for induction of general anaesthesia.
Mechanism of Action
It is thought that the actions of benzodiazepines such as midazolam are mediated through the inhibitory neurotransmitter gamma-aminobutyric acid (GABA), which is one of the major inhibitory neurotransmitters in the brain. Benzodiazepines increase the activity of GABA, thereby producing a calming effect, relaxing skeletal muscles, and inducing sleep. Benzodiazepines bind to the benzodiazepine site on GABA-A receptors, which potentiates the effects of GABA by increasing the frequency of chloride channel opening.
Midazolam is a short-acting benzodiazepine central nervous system (CNS) depressant. Pharmacodynamic properties of midazolam and its metabolites, which are similar to those of other benzodiazepines, include sedative, anxiolytic, amnesic and hypnotic activities. Benzodiazepine pharmacologic effects appear to result from reversible interactions with the (gamma)-amino butyric acid (GABA) benzodiazepine receptor in the CNS, the major inhibitory neurotransmitter in the central nervous system. The action of midazolam is readily reversed by the benzodiazepine receptor antagonist, flumazenil.
Rapidly absorbed after oral administration. The absolute bioavailability of the midazolam syrup in pediatric patients is about 36%. The absolute bioavailability, if given intramuscularly (IM), is greater than 90%. Cmax, IM = 90 ng/mL; Tmax, IM = 0.5 hours. Following IM administered, Cmax for midazolam and its 1-hydroxy metabolite were approxiately one-half of those achieved after intravenous injection.
* 1.24 to 2.02 L/kg [pediatric patients (6 months to <16 years) receiving 0.15 mg/kg IV midazolam,] * 1 to 3.1 L/kg [intravenously administered, healthy adults] Female gender, old age, and obesity may increase the volume of distribution. Midazolam may also cross the placenta and has been detected in human milk and cerebrospinal fluid.
Midazolam is primarily metabolized in the liver and gut by human cytochrome P450 IIIA4 (CYP3A4) to its pharmacologic active metabolite, (alpha)-hydroxymidazolam (also known as 1-hydroxy-midazolam), and 4-hydroxymidazolam (makes up 5% or less of the biotransformation products). 1-hydroxy-midazolam is at least as potent as the parent compound and may contributed to the overall activity of midazolam. In vitro studies have demonstrated that the affinities of 1- and 4-hydroxy-midazolam for the benzodiazepine receptor are approximately 20% and 7%, respectively, relative to midazolam. It also undergoes N-glucuronidation via UGT1A4.
Midazolam is primarily metabolized in the liver and gut by human cytochrome P450 IIIA4 (CYP3A4) to its pharmacologic active metabolite, α-hydroxymidazolam, followed by glucuronidation of the α–hydroxyl metabolite which is present in unconjugated and conjugated forms in human plasma. The α- hydroxymidazolam glucuronide is then excreted in urine. No significant amount of parent drug or metabolites is extractable from urine before beta-glucuronidase and sulfatase deconjugation, indicating that the urinary metabolites are excreted mainly as conjugates. The amount of midazolam excreted unchanged in the urine when given intravenously is less than 0.5%. 45% to 57% of the dose was excreted in the urine as 1-hydroxymethyl midazolam conjugate.
Intravenous, healthy adults = 1.8 to 6.4 hours (mean of 3 hours)
* 9.3 to 11 mL/min/kg [pediatric patients (6 months to <16 years old)] * 0.25 to 0.54 L/hr/kg [intravenous, healthy adults]
LD50=825 mg/kg (Orally in rats). Signs of overdose include sedation, somnolence, confusion, impaired coordination, diminished reflexes, coma, and deleterious effects on vital signs.
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