MIDOZALAM HYDROCHLORIDE
Clinical safety rating: caution
Comprehensive clinical and safety monograph for MIDOZALAM HYDROCHLORIDE (MIDOZALAM HYDROCHLORIDE).
Midazolam hydrochloride is a benzodiazepine that enhances the effect of the neurotransmitter gamma-aminobutyric acid (GABA) at the GABA-A receptor, resulting in increased chloride ion conductance, neuronal hyperpolarization, and inhibition of neuronal transmission. This produces sedative, anxiolytic, amnestic, and anticonvulsant effects.
| Metabolism | Midazolam is primarily metabolized by the hepatic cytochrome P450 enzyme CYP3A4 to the active metabolite 1-hydroxymidazolam (also known as alpha-hydroxymidazolam), which is further conjugated. CYP3A5 may also contribute. The drug undergoes extensive first-pass metabolism after oral administration. |
| Excretion | Renal excretion of metabolites (approximately 90% as glucuronide conjugates, with less than 1% unchanged drug) and biliary/fecal excretion (approximately 5-10%). |
| Half-life | Terminal elimination half-life: 1.5-3 hours in healthy adults; prolonged in elderly (up to 6 hours), obesity, hepatic cirrhosis (up to 20 hours), and congestive heart failure. |
| Protein binding | 97-98% bound to serum albumin. |
| Volume of Distribution | 1.2-2.4 L/kg; increased in obesity (up to 3-5 L/kg) indicating extensive tissue distribution. |
| Bioavailability | Oral: 35-44% (first-pass effect); IM: 80-100%; Intranasal: 55-65%; Rectal: 40-80%. |
| Onset of Action | IV: 1-2 minutes; IM: 5-15 minutes; Oral: 15-30 minutes; Intranasal: 10-15 minutes; Rectal: 10-20 minutes. |
| Duration of Action | IV: 15-30 minutes (sedation), 20-60 minutes (anticonvulsant); IM: 60-90 minutes; Oral: 2-6 hours; clinical effects may be shorter due to redistribution. |
2.5-10 mg IV bolus for induction; 0.05-0.2 mg/kg/h IV infusion for sedation. IM: 0.07-0.08 mg/kg (max 5 mg) 30-60 min pre-procedure.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for GFR >50 mL/min. For GFR 10-50 mL/min: consider dose reduction by 25-50% due to prolonged effect. For GFR <10 mL/min: avoid use or use with extreme caution; no specific guidelines exist. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: avoid use or reduce dose by 75% with close monitoring. |
| Pediatric use | 0.05-0.2 mg/kg IV (max 5 mg) for induction. For sedation: 0.15-0.2 mg/kg IM (max 10 mg) or 0.5-0.75 mg/kg oral (max 20 mg). IV infusion: 0.02-0.1 mg/kg/h titrated. |
| Geriatric use | Reduce dose by 25-50% due to decreased clearance and increased sensitivity. Use lower initial doses (e.g., 1-2 mg IV) and titrate slowly. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
Comprehensive clinical and safety monograph for MIDOZALAM HYDROCHLORIDE (MIDOZALAM HYDROCHLORIDE).
| Breastfeeding | Midazolam is excreted into breast milk in small amounts (M/P ratio approximately 0.6). Due to potential for infant sedation and respiratory depression, avoid breastfeeding for at least 24 hours after administration or use with caution. |
| Teratogenic Risk | First trimester: Limited data; midazolam is not a known major teratogen but caution advised. Second and third trimesters: May cause fetal respiratory depression, hypotonia, and withdrawal symptoms if used chronically or near term. |
■ FDA Black Box Warning
Midazolam has a boxed warning for the risk of respiratory depression and death when used for sedation in non-intubated patients. It requires careful monitoring of respiratory function. Concomitant use with opioids or other central nervous system depressants increases the risk of profound sedation, respiratory depression, coma, and death.
| Serious Effects |
["Hypersensitivity to midazolam or any benzodiazepine","Acute narrow-angle glaucoma (due to anticholinergic effects)","Severe respiratory insufficiency (e.g., untreated sleep apnea, COPD with hypercapnia)","Concomitant use with nefazodone (CYP3A4 inhibitor) in oral formulations","Myasthenia gravis (relative contraindication due to muscle relaxant effects)"]
| Precautions | ["Respiratory depression: especially with rapid IV administration or high doses; monitor oxygen saturation and respiratory rate.","Risk of hypotension and cardiac arrest, particularly in critically ill patients.","Paradoxical reactions: agitation, aggression, hallucinations (more common in children and the elderly).","Physical dependence and withdrawal syndrome with prolonged use.","Impairment of ability to drive or operate machinery.","Elderly or debilitated patients: increased sensitivity and risk of adverse effects; reduce dosage."] |
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| Fetal Monitoring |
| Monitor maternal respiratory rate, oxygen saturation, and sedation level. Fetal heart rate monitoring if used during labor. Neonatal observation for respiratory depression and hypotonia if used near delivery. |
| Fertility Effects | No specific human data; animal studies suggest no significant impact on fertility at therapeutic doses. |