MIDAZOLAM HYDROCHLORIDE (AUTOINJECTOR)
Clinical safety rating: avoid
CNS depressants including alcohol and opioids increase sedation risk Can cause profound respiratory depression and hypotension.
Midazolam is a short-acting benzodiazepine that potentiates GABA-A receptor activity by binding to the benzodiazepine site, enhancing chloride ion conductance and neuronal hyperpolarization, leading to anxiolytic, sedative, amnestic, anticonvulsant, and muscle relaxant effects.
| Metabolism | Primarily metabolized by cytochrome P450 3A4 (CYP3A4) and, to a lesser extent, by CYP3A5. The major metabolite is 1-hydroxymidazolam (active). |
| Excretion | Renal excretion of metabolites (glucuronide conjugates) accounts for approximately 90% of elimination; less than 1% excreted unchanged; minimal fecal excretion (< 5%). |
| Half-life | Terminal elimination half-life is 1.8–6.4 hours (mean ~3 hours) in healthy adults; prolonged in elderly, obese, hepatic impairment (up to 15–20 hours), and critical illness. |
| Protein binding | ~97% bound to albumin. |
| Volume of Distribution | 1–3 L/kg (mean ~1.5 L/kg) indicating extensive tissue distribution; increased in obesity and critical illness. |
| Bioavailability | IM: >90%; oral: ~40% (due to extensive first-pass metabolism); nasal: ~50–80% (variable). |
| Onset of Action | IM (autoinjector): 15–30 minutes; IV: 1–2 minutes; nasal: 10–15 minutes; oral: 30–60 minutes. |
| Duration of Action | Sedation/anxiolysis: 1–2 hours after IV/IM; can be prolonged with hepatic/renal impairment or repetitive dosing due to active metabolites (α-hydroxymidazolam). |
10 mg intramuscularly once via autoinjector for acute seizure control.
| Dosage form | SOLUTION |
| Renal impairment | No specific dose adjustment recommended; use with caution in severe renal impairment (CrCl <30 mL/min) due to prolonged sedative effects. |
| Liver impairment | Child-Pugh A: no adjustment; Child-Pugh B: reduce dose by 50%; Child-Pugh C: contraindicated. |
| Pediatric use | Not FDA-approved for pediatric use via autoinjector; alternative formulations (e.g., buccal or intravenous) are preferred. Weight-based dosing for status epilepticus: 0.2 mg/kg IM (max 10 mg) per current guidelines. |
| Geriatric use | Reduce dose by 50% due to increased sensitivity and prolonged half-life; monitor for excessive sedation and respiratory depression. |
| 1st trimester | Consult provider |
| 2nd trimester | Consult provider |
| 3rd trimester | Consult provider |
Clinical note
CNS depressants including alcohol and opioids increase sedation risk Can cause profound respiratory depression and hypotension.
| FDA category | Positive |
| Breastfeeding | Midazolam is excreted into breast milk. M/P ratio is approximately 0.60. Due to infant sedation and feeding difficulties, caution is advised; use lowest dose and shortest duration if necessary. Monitor infant for drowsiness and feeding problems. |
| Teratogenic Risk | Midazolam is a benzodiazepine. First trimester: increased risk of congenital malformations (e.g., oral cleft) based on case-control studies; avoid use. Second/third trimesters: risk of fetal CNS depression, respiratory depression, and hypotonia (floppy infant syndrome) with prenatal exposure. Use only if clearly needed. |
■ FDA Black Box Warning
Risk of respiratory depression and apnea, especially when used with opioids or other CNS depressants. Resuscitative equipment and personnel trained in airway management must be immediately available. Do not administer by rapid IV bolus. Use in neonates may cause severe hypotension and seizures. Concomitant use with alcohol or opioids may result in profound sedation, respiratory depression, coma, or death.
| Common Effects | anesthesia |
| Serious Effects |
["Hypersensitivity to midazolam or benzodiazepines","Acute narrow-angle glaucoma","Severe respiratory insufficiency (e.g., COPD with hypercapnia)","Concurrent use with potent CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, ritonavir) without dose adjustment"]
| Precautions | ["Respiratory depression and arrest","Hypotension, especially in neonates and elderly","Paradoxical reactions (agitation, aggression)","Dependence and withdrawal","Use with caution in hepatic impairment, renal impairment, obesity, and myasthenia gravis","Not recommended for prolonged use in neonates due to benzyl alcohol content"] |
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| Fetal Monitoring | Monitor maternal respiratory rate, oxygen saturation, and level of sedation. Fetal heart rate monitoring is recommended, especially near term. Neonatal monitoring for respiratory depression, hypotonia, and sedation after delivery. |
| Fertility Effects | Animal studies do not indicate impaired fertility. Human data limited; no established effect on fertility. |