Pharmacology · Benzodiazepines
Midazolam !
A short-acting benzodiazepine for sedation in procedures and intensive care. Given IV it can stop breathing, so it needs continuous monitoring.
Updated 2026-11-01
The figure shows diazepam, a benzodiazepine that occupies the same site, bound to the human GABA-A receptor (α1β2γ2) with GABA; no structure with midazolam is available.
Mechanism of action
Midazolam binds the benzodiazepine site of the GABA-A receptor and makes GABA open the chloride channel more often. It acts quickly, giving sedation, anxiety relief and amnesia for the procedure. CYP3A4 breaks it down to alpha-hydroxymidazolam, which may add to its effect.
- Binds the benzodiazepine site of the GABA-A receptor
- GABA opens the chloride channel more often
- Rapid sedation, anxiety relief and amnesia
- CYP3A4 breaks it down; the effect wears off in hours
Pharmacokinetics
- Metabolism
- In the liver by CYP3A4 to alpha-hydroxymidazolam
- Half-life
- About 3 hours on average in healthy adults (range about 1.8 to 6.4); much longer in seriously ill newborns
- Onset and duration
- Sedation within about 3 to 5 minutes after IV injection
Indications
- Sedation, anxiety relief and amnesia before surgery
- Sedation for diagnostic, therapeutic and endoscopic procedures
- Induction of general anaesthesia
- Continuous sedation of intubated, ventilated patients in intensive care
Adverse effects
Common
- Drop in breathing rate and depth
- Low blood pressure
- Hiccups, nausea and vomiting
- Pain at the injection site
- Paradoxical agitation
Contraindications
- Hypersensitivity to midazolam
- Acute narrow-angle glaucoma
Key interactions
- Opioids
- Profound sedation, respiratory depression, coma and death
- Alcohol and other central nervous system depressants
- Additive sedation and breathing depression
- CYP3A4 inhibitors (erythromycin, diltiazem, verapamil, ketoconazole, itraconazole, cimetidine)
- Slower clearance and prolonged sedation
What is monitored
- Continuous pulse oximetry and breathing; capnography where available
- Heart rate and blood pressure
- Sedation level with a sedation scale
- Recovery before discharge after a procedure
Administration and safety
- Used only where breathing and heart function can be watched continuously, with resuscitation equipment and trained staff
- IV doses are individualised and titrated slowly; never a rapid push in newborns
- Several strengths exist: concentration is double-checked before drawing up
- Opioid doses are reduced when given together
Nursing care
- Baseline vital signs, oxygen saturation and airway assessment before sedation
- Watch breathing continuously during and after the dose
- Have flumazenil, oxygen and a bag-valve mask at the bedside
- Teach that memory of the procedure may be lost and that driving is avoided afterwards
Pregnancy and breastfeeding
Use late in pregnancy can cause sedation and withdrawal symptoms in the newborn, who is watched after birth.
Test yourself
Think of the answer, then tap the question to see it.
Why is IV midazolam a high-alert medicine?
It can cause respiratory depression and arrest; it needs continuous monitoring and rescue equipment.
Which enzyme breaks down midazolam, and what happens with erythromycin?
CYP3A4; erythromycin slows its clearance and prolongs sedation.
What can rapid IV midazolam cause in newborns?
Severe hypotension and seizures, especially with fentanyl.
Related drugs
← Back to the class: Benzodiazepines
Educational content on how drugs work; not a prescribing guide and no substitute for a health professional's advice. No doses are given.
Sources: DailyMed - MIDAZOLAM- midazolam hydrochloride injection, solution (DailyMed (U.S. National Library of Medicine), 2026); ATCDDD - ATC/DDD Index (WHO Collaborating Centre for Drug Statistics Methodology, 2026); Goodman & Gilman's The Pharmacological Basis of Therapeutics, 14th ed., ch. 22 (McGraw Hill, 2023).
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Representative model, for educational purposes only.