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. |
| Molecular Weight | 325.77 |
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 | Avoid. Midazolam is a benzodiazepine. First trimester exposure may be associated with a small increased risk of oral clefts. Use only if clearly needed. |
| 2nd trimester | Use with caution. May cause fetal sedation and withdrawal symptoms. Avoid prolonged use or high doses. |
| 3rd trimester | Avoid near term. May cause floppy infant syndrome (hypotonia, respiratory depression, feeding difficulties) if used near delivery. Use only if essential. |
Clinical note
Comprehensive clinical and safety monograph for MIDOZALAM HYDROCHLORIDE (MIDOZALAM HYDROCHLORIDE).
| Placental transfer | Complete placental transfer. Midazolam crosses the placenta rapidly, with cord blood concentrations approximately 40-50% of maternal plasma levels. |
| Breastfeeding | Midazolam enters breast milk in low concentrations. Short-term use appears compatible with breastfeeding. Monitor infant for sedation, respiratory depression, or feeding difficulties. Avoid repeated or high doses. American Academy of Pediatrics rates as 'usually compatible'. |
■ 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 benzodiazepineAcute narrow-angle glaucomaSevere hepatic impairment (Child-Pugh class C) without dose adjustment capabilities
| 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. |
| Food/Dietary |
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| Lactation Rating | L2 |
| 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. |
| 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. |
| Grapefruit and grapefruit juice inhibit CYP3A4 and can increase midazolam levels, leading to prolonged sedation; avoid consumption during therapy. There are no significant interactions with other foods. |
| Clinical Pearls | Midazolam hydrochloride is a short-acting benzodiazepine used for sedation, anxiolysis, and amnesia. It undergoes extensive hepatic metabolism via CYP3A4; dose reduction is required in hepatic impairment. Paradoxical reactions (e.g., agitation, aggression) can occur, especially in children and elderly. Flumazenil is the reversal agent. Monitor respiratory depression, especially when combined with opioids. Intramuscular injection is an alternative for patients with poor IV access, but absorption is slower. In elderly, reduce dose by 50% due to increased sensitivity. Midazolam is highly protein bound; displacement interactions with valproic acid can increase free fraction. |
| Patient Advice | Midazolam may cause drowsiness, dizziness, and coordination problems; avoid driving or operating machinery for 24 hours after administration. · Alcohol can intensify sedative effects; avoid alcohol for at least 24 hours after use. · Inform your healthcare provider if you are pregnant, breastfeeding, or have a history of drug or alcohol abuse. · You may experience temporary memory loss for events during the procedure; this is a known effect. · Midazolam can cause injection site pain; report any signs of infection or severe discomfort. |