| Item |
Information |
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Drug Groups
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illicit; approved |
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Description
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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. |
| Indication |
For use as a sedative perioperatively. |
| Pharmacology |
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. |
| Toxicity |
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. |
| Affected Organisms |
| • |
Humans and other mammals |
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| Biotransformation |
Midazolam is primarily metabolized in the liver and gut by human cytochrome P450 IIIA4 (CYP3A4) to its pharmacologic active metabolite, (alpha)-hydroxymidazolam, and 4-hydroxymidazolam. |
| Absorption |
Rapidly absorbed after oral administration (absolute bioavailability of the midazolam syrup in pediatric patients is about 36%, and intramuscular is greater than 90%). |
| Half Life |
2.2-6.8 hours |
| Protein Binding |
97% |
| Elimination |
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. |
| Distribution |
* 1.24 to 2.02 L/kg [pediatric patients (6 months to <16 years) receiving 0.15 mg/kg IV midazolam,] |
| Clearance |
* 9.3 to 11 mL/min/kg [pediatric patients (6 months to <16 years old)] |
| References |
| • |
Skerritt JH, Johnston GA: Enhancement of GABA binding by benzodiazepines and related anxiolytics. Eur J Pharmacol. 1983 May 6;89(3-4):193-8.
[Pubmed]
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Isojarvi JI, Tokola RA: Benzodiazepines in the treatment of epilepsy in people with intellectual disability. J Intellect Disabil Res. 1998 Dec;42 Suppl 1:80-92.
[Pubmed]
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Garratt JC, Gent JP, Feely M, Haigh JR: Can benzodiazepines be classified by characterising their anticonvulsant tolerance-inducing potential? Eur J Pharmacol. 1988 Jan 5;145(1):75-80.
[Pubmed]
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Tokunaga S, Takeda Y, Shinomiya K, Hirase M, Kamei C: Effects of some H1-antagonists on the sleep-wake cycle in sleep-disturbed rats. J Pharmacol Sci. 2007 Feb;103(2):201-6. Epub 2007 Feb 8.
[Pubmed]
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Vermeeren A: Residual effects of hypnotics: epidemiology and clinical implications. CNS Drugs. 2004;18(5):297-328.
[Pubmed]
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