MIDAZOLAM HYDROCHLORIDE
Clinical safety rating: avoid
CNS depressants including alcohol and opioids increase sedation risk Can cause profound respiratory depression and hypotension.
Benzodiazepine agonist at GABA-A receptors, enhancing chloride influx and neuronal hyperpolarization, leading to anxiolytic, sedative, hypnotic, anticonvulsant, and muscle relaxant effects.
| Metabolism | Hepatic via CYP3A4 and CYP3A5; major metabolite is 1-hydroxymidazolam (active). |
| Excretion | Renal: <1% unchanged; hepatic metabolism to 1-hydroxymidazolam (active) and other metabolites, excreted primarily in urine (60-80%) as glucuronide conjugates, and about 2-10% in feces. |
| Half-life | Terminal elimination half-life: 1.5-3.5 hours (range 1-12 hours) in healthy adults; prolonged in elderly (5-6 hours), obese, hepatic impairment (up to 20 hours), and critical illness (up to 12 hours). Context: short-acting benzodiazepine; half-life supports use for procedural sedation and ICU sedation, but accumulation can occur with prolonged infusions. |
| Protein binding | Approximately 94-97% bound to serum albumin, primarily to albumin; also binds to alpha1-acid glycoprotein. |
| Volume of Distribution | 1-2.5 L/kg; increases with age (elderly: 2-4 L/kg), obesity (up to 5 L/kg), and critical illness (up to 7 L/kg). Clinical meaning: high Vd indicates extensive tissue distribution; loading doses required for rapid effect. |
| Bioavailability | Oral: ~36-44% (first-pass effect); IM: >90%; Intranasal: ~50-83% with wide interindividual variability; Rectal: ~25-50%. |
| Onset of Action | IV: 1-2 minutes; IM: 5-15 minutes; Intranasal: 10-15 minutes; Oral: 15-30 minutes; Rectal: 10-20 minutes. |
| Duration of Action | IV: 20-30 minutes (sedation) with recovery in 1-2 hours; IM: 1-1.5 hours; Oral: peak effect 1 hour, duration 2-6 hours (dose-dependent); Intranasal: 20-30 minutes sedation, recovery 30-60 minutes. Note: duration may be shorter in children due to faster clearance. |
| Molecular Weight | 362.25 |
Adults: IV: 0.5-2 mg slow IV over 2 minutes, may repeat q2-3min; IM: 0.07-0.08 mg/kg (usual total 2-3 mg); oral: 7.5-15 mg once. For sedation, titrate to effect.
| Dosage form | INJECTABLE |
| Renal impairment | No dose adjustment required for mild-moderate renal impairment. For severe renal impairment (CrCl <30 mL/min), consider dose reduction by 50% and monitor for prolonged sedation. |
| Liver impairment | Child-Pugh A: No adjustment. Child-Pugh B: Reduce dose by 50%. Child-Pugh C: Contraindicated or use with extreme caution; consider alternative. |
| Pediatric use | IV sedation: 0.05-0.1 mg/kg (max 6 mg) slow IV over 2-3 minutes; titrate. Oral: 0.25-0.5 mg/kg (max 20 mg) 30-60 min before procedure. Intranasal: 0.2-0.3 mg/kg. For neonates, use lower doses and monitor. |
| Geriatric use | Reduce initial dose by 50% (e.g., IV: 0.25-0.5 mg; oral: 3.75-7.5 mg). Titrate slowly to avoid hypotension, respiratory depression, and prolonged sedation. Avoid doses > 5 mg IV in elderly. |
| 1st trimester | Limited data; human studies suggest possible increased risk of congenital malformations after first trimester exposure; generally avoided unless necessary. |
| 2nd trimester | Fetal sedation and withdrawal risks; use only if clearly needed and benefits outweigh risks. |
| 3rd trimester | Neonatal sedation, hypotonia, withdrawal, and respiratory depression if used near term; avoid prolonged or high-dose use. |
Clinical note
CNS depressants including alcohol and opioids increase sedation risk Can cause profound respiratory depression and hypotension.
| FDA category | Positive |
| Placental transfer | Rapidly crosses the placenta; cord blood concentrations 50-100% of maternal serum levels. |
| Breastfeeding |
■ FDA Black Box Warning
Concurrent use of benzodiazepines and opioids may result in profound sedation, respiratory depression, coma, and death. Reserve concomitant prescribing for patients for whom alternative treatment options are inadequate.
| Common Effects | anesthesia |
| Serious Effects |
Acute narrow-angle glaucomaSevere respiratory insufficiencyHypersensitivity to benzodiazepinesMyasthenia gravisSevere hepatic impairment (Child-Pugh Class C)
| Precautions | Respiratory depression, risk of hypotension particularly in children, paradoxical reactions (restlessness, agitation), dependence risk, withdrawal symptoms upon abrupt discontinuation, caution in hepatic impairment, renal impairment, myasthenia gravis, and COPD. |
| Food/Dietary | Grapefruit juice may increase midazolam plasma concentrations (inhibit CYP3A4). Avoid grapefruit products during therapy. No other significant food interactions. Alcohol must be strictly avoided. |
Loading safety data…
| Midazolam is excreted into breast milk in low concentrations; clinical significance is minimal with single doses, but repeated use may cause sedation in the infant. |
| Lactation Rating | L2 (Probably Compatible - Short-term use) |
| Teratogenic Risk | First trimester: Limited human data; animal studies show increased risk of cleft palate at high doses. Second and third trimesters: Risk of fetal sedation and withdrawal symptoms; use near term may cause neonatal respiratory depression and hypotonia. |
| Fetal Monitoring | Monitor maternal respiratory rate, oxygen saturation, sedation level, and blood pressure. Fetal heart rate monitoring recommended during prolonged or high-dose use, especially near term. |
| Fertility Effects | No significant adverse effects on fertility reported in animal studies; human data lacking. |
| Clinical Pearls | Midazolam is a short-acting benzodiazepine with rapid onset (1–2 min IV, 15–30 min IM). Flumazenil is the reversal agent. Use lower doses in elderly and cirrhotics due to prolonged clearance. Respiratory depression risk is dose-dependent and potentiated with opioids. NOT safe for prolonged sedation in ICU without ventilation due to accumulation of active metabolite (1-hydroxymidazolam glucuronide) in renal impairment. |
| Patient Advice | Do not drive or operate machinery for at least 24 hours after administration. · Avoid alcohol for 24-48 hours due to enhanced sedative effects. · Report any difficulty breathing, excessive drowsiness, or confusion immediately. · You may not remember the procedure (anterograde amnesia is expected). · Arrange for a responsible adult to escort you home after the procedure. |