Clinical Scenario: Breakthrough Partial Seizure in a Patient on Levetiracetam 1g BD, Now in ER with Biliary Colic

Immediate Assessment First (ABCs + Context)

• Airway, Breathing, Circulation - midazolam causes respiratory depression; monitor SpO2, be ready to support ventilation
• Check if the seizure has terminated after midazolam
• Note: 2 mg midazolam IV/IM is on the lower end of the therapeutic dose for seizure termination (standard is 0.1-0.2 mg/kg IV, or 0.2 mg/kg IM - so for a 60 kg patient, 0.2 mg/kg IV = 12 mg). 2 mg is a subtherapeutic dose for most adults and may not be sufficient

Step 1 - Is the Seizure Still Active?

• IV Lorazepam 0.1 mg/kg (e.g., 4-8 mg IV at 2 mg/min) - preferred in-hospital
• OR additional Midazolam 0.1-0.2 mg/kg IV (titrate to effect, total dose up to 10-15 mg in adults)

Step 2 - Second-Line IV Antiseizure Drug (Critical Next Step)

Best choice here: IV Levetiracetam 20-30 mg/kg (since she is already on it - boost to therapeutic levels; it has no significant drug interactions, no hepatic metabolism, and is safe in the biliary colic context)

Step 3 - Identify and Treat the Precipitating Cause of Breakthrough Seizure

1. Did she miss her levetiracetam dose? (most common cause of breakthrough) - correct with IV LEV
2. Pain itself - severe pain (biliary colic) is a physiological stressor that can lower seizure threshold
3. Metabolic derangements - check glucose, Na+, Ca2+, Mg2+, renal function (LEV is renally cleared - any AKI could alter levels unpredictably)
4. Sleep deprivation and stress from acute illness
5. Drug interactions - opioids or NSAIDs given for biliary colic do not significantly interact with LEV

• Serum electrolytes (Na, K, Ca, Mg, glucose)
• Renal function (Cr, BUN) - LEV is renally excreted; dose adjustment needed if GFR <50
• LFTs (relevant given biliary colic)
• CBCs
• Serum LEV levels if available
• ABG if respiratory compromise

Step 4 - Treat the Biliary Colic Simultaneously

• Analgesia: IV diclofenac 75 mg or butylscopolamine (buscopan) 20 mg IV are first-line for biliary colic
• Avoid morphine (can cause Oddi sphincter spasm); pethidine/meperidine is preferred opioid if needed
• Arrange HIDA scan or repeat USG to confirm diagnosis and rule out cholecystitis/choledocholithiasis
• Surgery/GI consult if cholecystitis confirmed

Step 5 - If Seizure Persists (Refractory SE)

• Established SE (30 min - 48 h): IV Midazolam infusion 0.2 mg/kg loading → 0.2-0.6 mg/kg/h, AND/OR IV Propofol 2 mg/kg → 2-10 mg/kg/h
• Requires ICU admission, intubation, continuous EEG monitoring
• Late refractory SE (>48 h): Pentobarbital/thiopental coma, ketamine, isoflurane

Step 6 - Review Long-Term Anticonvulsant Plan

• If LEV 1g BD is failing (breakthrough seizure), consider dose optimization (LEV can go up to 3g/day) OR add-on therapy (lacosamide, lamotrigine, carbamazepine for focal seizures)
• Neurology consult for chronic management review
• Review seizure diary, sleep, compliance, alcohol use

Summary Algorithm for This Patient

Midazolam 2 mg given → Assess if seizure stopped
        ↓
Seizure ongoing? → Repeat BZD (Lorazepam 4 mg IV or MDZ 0.1 mg/kg)
        ↓
Still ongoing? → IV Levetiracetam 20-30 mg/kg (preferred here) 
                 OR Phenytoin 20 mg/kg IV
        ↓
ABCs, labs, treat biliary colic (diclofenac/buscopan)
        ↓
ICU if refractory → MDZ/Propofol infusion