What PRN (pro re nata) medication is recommended for seizure management?

PRN Medications for Seizure Management

Benzodiazepines are the first-line PRN medications for acute seizure management, with intravenous lorazepam being the most effective option for rapid seizure cessation with fewer respiratory side effects than other options. For PRN seizure management, intravenous lorazepam (2-8 mg) or diazepam (5-20 mg) should be administered as first-line therapy, followed by phenytoin/fosphenytoin, valproate, or levetiracetam as second-line options if seizures persist. 1

First-Line PRN Medications

Benzodiazepines

1. Lorazepam (IV)

   • Dosage: 1-2 mg IV stat (up to maximum of 8 mg)
   • Advantages: Longer duration of action in the CNS compared to diazepam
   • Lower risk of respiratory depression compared to diazepam 1
   • Similar efficacy to diazepam for seizure cessation (RR 1.04) 2

2. Diazepam (IV/PR)

   • Dosage: 5-10 mg IV stat (up to maximum of 30 mg) 3
   • Rectal option: 0.2-0.5 mg/kg when IV access not available 4
   • Faster onset but shorter duration than lorazepam
   • Higher risk of respiratory depression

3. Midazolam (IM/Buccal/Intranasal)

   • Dosage: 2.5-5 mg IM/buccal/intranasal
   • Particularly useful when IV access is difficult
   • Intramuscular midazolam has been shown to be as effective as IV diazepam 2

Second-Line PRN Medications (if benzodiazepines fail)

Antiepileptic Drugs

1. Valproate (IV)

   • Dosage: 20-30 mg/kg IV at 5-6 mg/kg/min
   • Advantages: Similar efficacy to phenytoin but fewer cardiovascular side effects
   • 88% seizure cessation rate within 20 minutes of infusion 1
   • Less hypotension compared to phenytoin (0% vs 12%) 1

2. Phenytoin/Fosphenytoin (IV)

   • Dosage: 18-20 mg/kg IV phenytoin or equivalent fosphenytoin
   • Traditional second-line agent
   • Limitations: Only 56% success rate in terminating status epilepticus when used after benzodiazepines 1
   • Risk of hypotension and cardiac arrhythmias

3. Levetiracetam (IV)

   • Dosage: 20-30 mg/kg IV
   • Similar efficacy to valproate (73% vs 68%) in refractory status epilepticus 1
   • Favorable side effect profile, minimal drug interactions

Algorithm for PRN Seizure Management

1. Immediate Assessment (0-5 minutes)

   • Ensure airway, breathing, circulation
   • Position patient to prevent injury
   • Time the seizure

2. First-Line Treatment (5-10 minutes)

   • Administer IV lorazepam 2 mg (preferred) or diazepam 5-10 mg
   • If IV access unavailable, use rectal diazepam, buccal/intranasal midazolam, or IM midazolam

3. Second-Line Treatment (if seizure continues >10 minutes)

   • Administer IV valproate 20-30 mg/kg (preferred due to better safety profile)
   • Alternative: IV phenytoin/fosphenytoin 18-20 mg/kg or levetiracetam 20-30 mg/kg

4. Refractory Status (if seizure continues >30 minutes)

   • Consider ICU admission and anesthetic doses of midazolam, propofol, or barbiturates 1

Important Clinical Considerations

• Respiratory monitoring is essential with benzodiazepine administration; respiratory depression occurs in up to 18% of patients 2
• Cardiovascular monitoring is particularly important with phenytoin/fosphenytoin due to risk of hypotension and arrhythmias
• Timing is critical - seizures lasting >5 minutes should be treated as potential status epilepticus 2
• Route of administration should be chosen based on available access and urgency:
  • IV provides fastest onset but may delay treatment if access is difficult
  • IM, buccal, or intranasal routes are reasonable alternatives when IV access is challenging

Common Pitfalls to Avoid

1. Delayed treatment - seizures lasting >30 minutes significantly increase morbidity and mortality
2. Inadequate dosing - underdosing benzodiazepines is common and reduces efficacy
3. Failure to prepare for respiratory depression - always have resuscitation equipment available
4. Not considering drug interactions - particularly with phenytoin
5. Overlooking treatable causes - always search for underlying etiology (hypoglycemia, hyponatremia, drug toxicity, infection) 1