Midazolam Dosing for Acute Seizures
For acute seizures in adults and children, administer midazolam 0.2 mg/kg intramuscularly (maximum 6 mg per dose) when IV access is unavailable, or 0.05-0.10 mg/kg IV (maximum 4 mg per dose) when IV access is established, with doses repeated every 10-15 minutes as needed for continued seizures. 1
Route-Specific Dosing Algorithm
Intramuscular Route (Preferred When IV Access Unavailable)
- Administer 0.2 mg/kg IM (maximum 6 mg per dose) as first-line treatment when intravenous access is not immediately available. 1
- Repeat the same dose every 10-15 minutes if seizures persist. 1
- IM midazolam demonstrates superior effectiveness compared to IV lorazepam in prehospital settings, with 73.4% seizure cessation versus 63.4% (p<0.001). 2
- Onset of action occurs within approximately 5 minutes after IM administration. 1
Intravenous Route (When IV Access Established)
- Initial dose: 0.05-0.10 mg/kg administered slowly over 2-3 minutes (maximum single dose: 5 mg for sedation, 4 mg for status epilepticus). 1, 3
- Peak effect occurs at 3-5 minutes after administration. 1, 3
- Repeat doses every 10-15 minutes if needed for continued seizures. 1
- For rapid sequence intubation adjunct in seizure patients, use 0.2 mg/kg IV, allowing 2-3 minutes for effect before administering muscle relaxant. 1
Intranasal Route (Alternative)
- Administer 0.2 mg/kg intranasally (maximum 6 mg per dose) when other routes are not feasible. 4
- Recent real-world data suggests intranasal administration may be less effective than IM route, with a 6.5% increased risk of requiring rescue therapy compared to IM administration. 5
- However, intranasal route shows the highest satisfaction rate among caregivers in pediatric studies. 6
Escalation for Refractory Status Epilepticus
Loading Dose for Refractory Seizures
- Administer 0.15-0.20 mg/kg IV as a loading dose for seizures that persist despite initial bolus doses. 4, 7
- This loading dose should be given over at least 2-3 minutes in intubated patients. 3
Continuous Infusion Protocol
- Start continuous infusion at 1 μg/kg/min (0.06 mg/kg/hr) following the loading dose. 4, 7
- Titrate by increments of 1 μg/kg/min every 15 minutes up to a maximum of 5 μg/kg/min (0.3 mg/kg/hr) until seizures stop. 4, 7
- For adults, the usual maintenance infusion rate is 0.02-0.10 mg/kg/hr (1-7 mg/hr). 3
- Decrease the infusion rate by 10-25% every few hours to find the minimum effective rate and minimize accumulation. 3
Pediatric-Specific Considerations
Age-Based Dosing Adjustments
- Pediatric patients less than 6 years old may require higher doses (mg/kg) than older children and adults. 1, 3
- Pediatric patients 6 months to 5 years: Initial IV dose 0.05-0.1 mg/kg; total dose up to 0.6 mg/kg may be necessary (usually not exceeding 6 mg). 3, 8
- Pediatric patients 6-12 years: Initial IV dose 0.025-0.05 mg/kg; total dose up to 0.4 mg/kg may be needed (usually not exceeding 10 mg). 3, 8
- Pediatric patients 12-16 years: Dose as adults, though total dose usually does not exceed 10 mg. 3, 8
- For IM administration in pediatrics, doses of 0.1-0.15 mg/kg are usually effective; for more anxious patients, doses up to 0.5 mg/kg have been used (total dose usually not exceeding 10 mg). 3, 8
Special Pediatric Populations
- Infants less than 6 months are particularly vulnerable to airway obstruction and hypoventilation; titrate with small increments and monitor closely. 3, 8
- In obese pediatric patients, calculate the dose based on ideal body weight. 1
Critical Safety Monitoring
Respiratory Monitoring Requirements
- Monitor oxygen saturation continuously regardless of administration route, as there is an increased risk of apnea, especially when combined with other sedative agents or opioids. 1, 4, 7
- Be prepared to provide respiratory support including bag-valve-mask ventilation and potential intubation. 1, 4, 7
- Assisted ventilation is recommended for pediatric patients receiving other CNS depressant medications such as opioids. 3, 8
Reversal Agent Availability
- Have flumazenil available to reverse life-threatening respiratory depression caused by midazolam. 1, 4, 7
- However, flumazenil will also counteract the anticonvulsant effects and may precipitate recurrence of seizures. 1
Hemodynamic Monitoring
- Monitor for hypotension, especially when administered rapidly. 7
- Rapid infusion may cause myocardial depression and hypotension. 1
Dose Modifications and Drug Interactions
Concomitant Medication Adjustments
- Reduce all midazolam doses by 30-50% when combined with opioids or other CNS depressants. 4
- When midazolam is given with an opioid, the initial dose of each must be reduced. 3, 8
- Patients with residual effects from anesthetic drugs or those concurrently receiving other sedatives require the lowest recommended doses. 3
Special Patient Populations
- Patients with hepatic impairment require dose reduction due to decreased clearance. 4, 7
- Higher risk or debilitated patients may require lower dosages whether or not concomitant sedating medications have been administered. 3, 8
Common Pitfalls and Caveats
Dosing Errors to Avoid
- Lower doses of midazolam (below 0.2 mg/kg) are ineffective for rapid sequence intubation in seizure patients. 1
- Real-world data shows that higher doses are associated with lower risk of rescue therapy (risk difference -2.6% per mg/kg increase). 5
- Avoid rapid IV administration to prevent oversedation and hypotension. 7
Timing Considerations
- Allow sufficient time (2-3 minutes) for midazolam to take effect before repeating doses or administering additional medications. 1, 3
- Midazolam takes approximately three times longer than diazepam to achieve peak EEG effects; wait an additional 2-3 minutes to fully evaluate sedative effect before repeating a dose. 3, 8
Route Selection Pitfalls
- Do not delay treatment attempting IV access when the IM or intranasal route is immediately available. 4
- IV midazolam is associated with an 11.1% decreased risk of rescue therapy compared to IM administration in real-world settings, but this advantage must be weighed against delays in establishing IV access. 5