What labs are needed in the emergency department (ED) for a known epileptic who has a seizure after missing a dose of Keppra (levetiracetam)?

Laboratory Testing for Known Epileptic with Seizure After Missed Keppra Dose

Basic laboratory tests should include serum levetiracetam (Keppra) level, complete blood count, comprehensive metabolic panel, and magnesium level for a known epileptic who has had a seizure after missing Keppra doses. 1

Priority Laboratory Tests

1. Serum levetiracetam (Keppra) level

   • Essential to determine current drug concentration
   • Therapeutic monitoring helps assess compliance and guide dosing
   • Normal therapeutic range should be documented

2. Complete Blood Count (CBC)

   • Monitor for potential hematologic abnormalities
   • Levetiracetam can rarely cause changes in WBC counts 2
   • Baseline values important for ongoing monitoring

3. Comprehensive Metabolic Panel (CMP)

   • Electrolytes (sodium, potassium, chloride, bicarbonate)
   • Renal function (BUN, creatinine) - important as levetiracetam is primarily renally excreted
   • Liver function tests (AST, ALT) - although levetiracetam has minimal hepatic metabolism 2
   • Glucose - to rule out hypoglycemia as a trigger for seizure

4. Magnesium level

   • Electrolyte disturbances can lower seizure threshold

Additional Considerations

• Calcium level - Electrolyte abnormalities can trigger seizures
• Toxicology screen - If substance use is suspected as contributing factor
• EEG - While not a laboratory test, consider if patient has altered mental status or status epilepticus is suspected

Management Algorithm

1. Assess seizure severity and current status

   • If actively seizing: follow status epilepticus protocol
   • If post-ictal: proceed with laboratory workup

2. Obtain laboratory studies

   • Draw all labs simultaneously to minimize patient discomfort
   • Prioritize tests based on clinical presentation

3. Administer levetiracetam loading dose if indicated

   • For adults: 30 mg/kg IV (maximum 2500 mg) administered over 10-15 minutes 3
   • For ongoing seizure activity after benzodiazepines: consider 30-50 mg/kg IV 3

4. Interpret results and adjust treatment

   • Low levetiracetam level: administer loading dose
   • Abnormal electrolytes: correct imbalances
   • Renal dysfunction: adjust maintenance dosing

Important Caveats

• Levetiracetam is primarily eliminated by renal excretion, so renal function tests are particularly important 2
• Unlike many other antiepileptic drugs, levetiracetam has minimal drug-drug interactions and doesn't require routine liver function monitoring 4
• Behavioral side effects can occur with levetiracetam; document any reported behavioral changes 4
• Recent research shows no significant difference in seizure termination rates between low (≤20 mg/kg), medium (21-39 mg/kg), and high (≥40 mg/kg) loading doses of levetiracetam, but higher doses were associated with increased intubation rates 5

Remember that while laboratory testing is important, the immediate priority is stabilizing the patient and preventing further seizures through appropriate medication administration.