- CNS depressant
- Short acting benzodiazepine (chemical class)
- Short acting benzodiazepine. CNS depressant with sedative, muscle relaxant, anticonvulsant.
- Estimated to be 2 - 4 times more potent than diazepam. Intensifies activity of gamma-aminobutyric acid (GABA), a major inhibitory neurotransmitter of the brain. This causes chloride channels to open allowing an influx of chloride (-ve ion) into the cell. This makes the neuronal cells hyperpolarized - i.e. it takes longer for the cells to reach threshold and depolarize. This results in CNS depression.
- Blocks memory, reduces anxiety, but enables patient to follow commands.
- Strong amnesic effects.
- Onset - 1 to 5 min (5-15 min IM)
- Peak - IV route unknown (45 min IM)
- Half-life -1.5 to 3 hours
- Duration - 2 to 6 hours (dose related)
Note: All benzodiazepines are metabolized by the liver. Midazolam is converted by the cytochrome P450 enzymes in the liver to a non-active metabolite. This is why Midazolam is shorter acting than diazepam.
- Sedation prior to intubation or electrical therapy.
- Sedation of intubated patients.
- Sedation of the agitated patients (provided a correctable underlying cause has been ruled out and the patient is stable).
- Hypersensitivity to midazolam or other benzodiazepines
- Acute narrow angle glaucoma
- Alcohol intoxication
- Depressed vital signs
- Use cautiously when administration of other CNS depressants / narcotics are being administered (Narcotic + Midazolam = Synergistic effect).
- Use cautiously in the elderly and those with renal disease.
- Use cautiously in cases of CHF / COPD (respiratory depressant effect).
- Over sedation, headache, blurred vision, paradoxical combativeness (rare).
- Hypotension, variations in pulse rate.
- Nausea, vomiting, hiccoughs.
- Pain and tenderness at injection site.
- Respiratory depression / arrest, cough.
Drug to Drug Interactions
- Drugs that are known to inhibit the cytochrome P450 enzyme system may increase the potency and duration of midazolam (i.e. some drugs in the drug classes of azole antimycotics, protease inhibitors, calcium channel antagonists, and macrolide antibiotics).
- Lower doses are necessary for patients receiving concomitant narcotics or other CNS depressants.
- Erythromycin, diltiazem, verapamil, ketoconazole, fluconazole and itraconazole were shown to significantly increase the bioavailability of midazolam and may cause prolonged sedation.
- Ritonavir and nelfinavir may cause intense and prolonged sedation and respiratory depression due to a decrease in plasma clearance of midazolam.
- Rifampin, carbamazepine, and phenytoin may markedly decreased the effectiveness of midazolam.
- 5 to 10 mg IM
- 2 to 5 mg IV/IO incrementally to effect.
- May be repeated as required in small increments.
- 0.1 mg/kg IV/IO (Max dose 5 mg)
- 0.2 mg/kg IM (Max dose 10 mg)
- Unlike Diazepam, Midazolam is the first water-soluble benzodiazepine that may be administered in any IV fluid.
- 2 mg of Midazolam is approximately equivalent to 5 mg of diazepam