MIDAZOLAM
Clinical safety rating: avoid
Positive evidence of fetus risks but benefits may outweigh risks in some cases
Midazolam is a benzodiazepine that potentiates gamma-aminobutyric acid (GABA) activity by binding to the benzodiazepine site on GABA-A receptors, enhancing GABA's inhibitory effects, leading to increased chloride ion conductance, hyperpolarization, and neuronal inhibition.
| Metabolism | Midazolam is extensively metabolized in the liver via CYP3A4 isoenzymes to active metabolites (1-hydroxymidazolam and 4-hydroxymidazolam), which undergo glucuronidation. |
| Excretion | Renal: approximately 45-57% as metabolites (primarily 1-hydroxymidazolam glucuronide) and <1% unchanged; fecal: 2-10% via biliary excretion. |
| Half-life | Terminal elimination half-life: 1.5-2.5 hours in healthy adults; prolonged in elderly (5-6 hours), obesity, hepatic cirrhosis (up to 20 hours), and critical illness. |
| Protein binding | 97% bound to albumin. |
| Volume of Distribution | Vd: 1-3 L/kg; increased in obesity (up to 3-5 L/kg) and critically ill patients, reflecting extensive tissue distribution. |
| Bioavailability | Oral: 40-50% (first-pass metabolism); IM: >90%; Intranasal: approximately 50-80%; Rectal: approximately 40-50%. |
| 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: 20-30 minutes (amnesia up to 1 hour); IM: 2-6 hours (dose-dependent); Oral: 2-6 hours; recovery may be prolonged in elderly or hepatic impairment. |
IV: 0.5-2 mg initial, titrate by 0.5-1 mg increments every 2-3 min; typical total 2.5-5 mg. IM: 0.07-0.08 mg/kg (usual 5 mg). Oral: 7.5-15 mg as a single premedication dose.
| Dosage form | SPRAY |
| Renal impairment | GFR ≥ 30 mL/min: no adjustment. GFR 10-29 mL/min: consider 25% dose reduction. GFR < 10 mL/min: avoid long-term use; consider 50% dose reduction or alternative. |
| Liver impairment | Child-Pugh A: no adjustment. Child-Pugh B: reduce dose by 50%. Child-Pugh C: use with caution; reduce dose by 75% or consider alternative. |
| Pediatric use | IV sedation: 0.05-0.1 mg/kg initial, max 0.15-0.2 mg/kg total. Oral premedication: 0.25-1 mg/kg (max 20 mg). Intranasal: 0.3 mg/kg (max 10 mg). Rectal: 0.3-0.5 mg/kg (max 20 mg). |
| Geriatric use | Initial dose: 0.5 mg IV; titrate slowly with 0.5 mg increments. Max dose: 1.5 mg total. Oral: 3-7.5 mg as a single dose. Avoid doses > 7.5 mg due to increased risk of oversedation 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.
| Breastfeeding | Midazolam is excreted into breast milk. The milk-to-plasma (M/P) ratio is approximately 0.15-0.47. Oral bioavailability in infants is low (poor oral absorption), so risk is likely minimal after single doses, but repeated or high-dose exposure may cause sedation in the infant. Alternative agents with shorter half-lives are preferred during lactation. |
| Teratogenic Risk | First trimester: Limited human data, but no consistent pattern of major malformations; benzodiazepines are associated with a small increased risk of oral cleft (about 0.2-0.4% absolute risk). Second and third trimesters: Risk of floppy infant syndrome, respiratory depression, hypotonia, and withdrawal symptoms in neonates, especially with chronic or high-dose exposure near term. |
■ FDA Black Box Warning
Midazolam is associated with respiratory depression, apnea, and respiratory arrest. Concomitant use with other CNS depressants (e.g., opioids, alcohol) increases risk. Should be administered only by trained personnel in a setting equipped for monitoring and resuscitation.
| Common Effects | anesthesia |
| Serious Effects |
["Hypersensitivity to midazolam or other benzodiazepines","Acute narrow-angle glaucoma","Severe hepatic impairment (Child-Pugh C)","Concurrent use with HIV protease inhibitors (e.g., atazanavir, ritonavir) or other potent CYP3A4 inhibitors (e.g., ketoconazole, itraconazole) unless monitored closely"]
| Precautions | ["Respiratory depression and apnea risk, especially in elderly, debilitated, or patients with COPD","Hypotension and cardiac arrest risk in critically ill patients","Paradoxical reactions (e.g., agitation, aggression)","Potential for abuse and dependence (Schedule IV controlled substance)","Use with caution in patients with hepatic or renal impairment","Risk of withdrawal symptoms with abrupt discontinuation","Concomitant use with opioids may cause profound sedation, respiratory depression, coma, and death"] |
Loading safety data…
| Fetal Monitoring | Monitor maternal sedation, respiratory rate, and oxygen saturation during administration. For chronic use or high doses near term, monitor fetal heart rate during labor and assess neonatal Apgar scores, respiratory status, hypotonia, and withdrawal symptoms (irritability, feeding difficulties) after birth. |
| Fertility Effects | No specific data on human fertility impairment; animal studies with benzodiazepines have not shown significant effects on fertility. However, benzodiazepines may influence hypothalamic-pituitary-gonadal axis, but relevance is unknown. |