What is the appropriate midazolam dose for an acute seizure in adults (≥18 years) and children (≥6 months to <18 years) via IV, IM, or intranasal routes?

Midazolam Dosing for Acute Seizures

For acute seizures, administer midazolam 0.2 mg/kg intranasally or buccally (maximum 10 mg), 0.1 mg/kg intramuscularly (maximum 10 mg), or 0.05-0.1 mg/kg intravenously (maximum 5 mg per dose), with the intranasal and intramuscular routes demonstrating equivalent efficacy and being preferred when IV access is unavailable. 1, 2, 3

Route-Specific Dosing

Intranasal Administration

• Dose: 0.2 mg/kg (maximum 10 mg per dose) 3, 4
• Achieves seizure cessation in 88-93% of cases within 10 minutes 5
• Mean time to seizure cessation: 50.6 seconds from administration 4
• Highest satisfaction rate among caregivers compared to other routes 5
• Local mucosal irritation occurs in less than one-third of cases 3

Intramuscular Administration

• Dose: 0.1 mg/kg (maximum 10 mg per dose) 6, 2
• Achieves seizure cessation in 85-94% of cases 5
• Equivalent efficacy to IV lorazepam 4 mg in prehospital status epilepticus for adults and children >40 kg 6
• Preferred over rectal diazepam when IV access is unavailable 6

Buccal Administration

• Dose: 0.3 mg/kg (maximum 10 mg per dose) 7
• Achieves seizure cessation in 78-91% of cases 5
• Mean time to cessation: 3.89 minutes (median 3 minutes) 7
• 100% efficacy for convulsions shorter than 30 minutes duration 7

Intravenous Administration

• Initial dose: 0.05-0.1 mg/kg (maximum 5 mg per dose) 2
• Administer slowly over 2-3 minutes 2
• For refractory status epilepticus: loading dose 0.15-0.20 mg/kg (7.5-10 mg), followed by continuous infusion starting at 0.06 mg/kg/hr (3 mg/hr) 2

Repeat Dosing Protocol

If seizures continue after initial dose, repeat every 5-10 minutes for a maximum of 2-3 doses before escalating to alternative therapies or seeking emergency care. 1

• Benzodiazepines are rapidly redistributed and seizures often recur within 15-20 minutes 6, 1
• Immediately follow midazolam with a long-acting anticonvulsant such as phenytoin/fosphenytoin or oral carbamazepine 6, 1
• If seizures persist after second dose, activate emergency medical services 1

Critical Safety Monitoring

Respiratory Precautions

• Monitor oxygen saturation and respiratory status continuously, especially with repeat dosing 1, 2
• Respiratory depression occurs in approximately 1% of cases but can develop up to 30 minutes after administration 2, 3
• Have flumazenil immediately available for reversal, though note it also counteracts anticonvulsant effects and may precipitate seizures 6, 2
• Position patient on their side to prevent aspiration 1

Dose Reductions Required

• Hepatic or renal impairment: Reduce dose by at least 20% 1, 2
• Concurrent CNS depressants (including opioids): Reduce dose by at least 20% 1, 2
• Elderly patients (≥60 years): Reduce dose by 20-50% 2
• Patients on H2-receptor antagonists: Reduce dose due to 30% increased bioavailability 2

Age-Specific Considerations

Pediatric Patients (≥6 months to <18 years)

• Same weight-based dosing as adults: 0.2 mg/kg intranasal, 0.1 mg/kg IM, 0.05-0.1 mg/kg IV 3, 5, 4
• Paradoxical agitation occurs in approximately 6% of younger children 2
• Intranasal midazolam 0.2 mg/kg is as effective as rectal diazepam 0.5 mg/kg in pediatric febrile and afebrile seizures 3

Adult Patients (≥18 years)

• Standard dosing applies unless patient is elderly, frail, or has comorbidities requiring dose reduction 2
• For adults >40 kg in status epilepticus, IM midazolam 10 mg shows equivalent efficacy to IV lorazepam 4 mg 6

Common Pitfalls to Avoid

• Failure to administer a long-acting anticonvulsant immediately after benzodiazepine, leading to seizure recurrence within 15-20 minutes 6, 1
• Inadequate time between doses: Wait full 5-10 minutes before repeat dosing to assess response 1
• Combining full doses with other CNS depressants without dose reduction, dramatically increasing respiratory depression risk 2
• Using IV route as first-line in prehospital setting: IM and intranasal routes are equally effective and faster to administer 6, 5
• Insufficient monitoring duration: Respiratory depression can occur up to 30 minutes post-administration 2, 3