What are the recommendations for intramuscular (IM) route in acute seizure management?

Intramuscular Route Recommendations for Acute Seizure Management

For acute seizure management, intramuscular (IM) midazolam is the preferred medication for the IM route due to its rapid absorption, excellent local tolerability, and effectiveness in terminating seizures within 5-10 minutes of administration. 1, 2

First-Line IM Medication Options

• Midazolam is the most effective IM medication for acute seizure management with rapid absorption from the injection site and excellent local tolerability 1
• IM midazolam dosing: 0.2 mg/kg (maximum: 6 mg per dose); may repeat every 10-15 minutes 3
• IM midazolam has been shown to be at least as effective as intravenous benzodiazepines in terminating seizures 2
• In a randomized trial comparing IM midazolam to IV lorazepam, seizures were absent on arrival to the emergency department in 73.4% of patients receiving IM midazolam compared to 63.4% with IV lorazepam (p<0.001 for superiority) 4

Important Considerations for IM Route

• IM diazepam should NOT be used due to erratic absorption and risk of tissue necrosis 3
• When IV access is not available, IM phenobarbital may be considered as an alternative when rectal diazepam is not possible due to medical or social reasons 3
• IM phenytoin should NOT be used for status epilepticus because peak serum levels may take up to 24 hours to achieve 5
• IM phenytoin carries significant risks of necrosis, abscess formation, and erratic absorption 5

Efficacy of IM Midazolam

• IM midazolam results in more rapid cessation of seizures compared to IV diazepam due to faster administration (7.8 ± 4.1 vs 11.2 ± 3.6 minutes, P = 0.047) 6
• In pediatric patients, IM midazolam has shown 94.2% effectiveness in stopping seizures in home settings and 85.3% in emergency room settings 7
• Pharmacodynamic effects of midazolam can be seen within seconds of administration, with seizure arrest usually attained within 5-10 minutes 1

Safety Considerations

• Monitor for respiratory depression when using IM midazolam, especially when combined with other sedative agents 3
• Be prepared to provide respiratory support regardless of route of administration 3
• Monitor oxygen saturation during and after IM midazolam administration 3
• Flumazenil may be administered to reverse life-threatening respiratory depression caused by benzodiazepines, but it will also reverse the anticonvulsant effects and may precipitate seizures 3

Treatment Algorithm for Acute Seizure Management Using IM Route

1. When IV access is not available, administer IM midazolam 0.2 mg/kg (maximum: 6 mg per dose) 3, 2
2. Monitor respiratory status and oxygen saturation 3
3. If seizures continue after 10-15 minutes, a second dose of IM midazolam may be administered 3
4. If seizures persist after two doses of IM midazolam, consider IM phenobarbital as a second-line agent 3
5. Continue efforts to establish IV access for administration of longer-acting anticonvulsants if needed 3
6. Once IV access is established, transition to IV benzodiazepines (lorazepam preferred over diazepam) followed by phenobarbital or phenytoin for sustained control 3

IM midazolam is particularly useful in physicians' offices, in the prehospital setting, and for patients with difficult IV access, making it the preferred choice for acute seizure management via the intramuscular route 1, 6.