Is Keppra (levetiracetam) the same as Dilantin (phenytoin)?

Keppra (Levetiracetam) and Dilantin (Phenytoin) Are Different Antiepileptic Medications

No, Keppra (levetiracetam) is not the same as Dilantin (phenytoin) - they are different antiepileptic medications with distinct mechanisms of action, side effect profiles, and clinical applications. 1

Key Differences Between Keppra and Dilantin

Mechanism of Action

• Keppra (levetiracetam) has a unique mechanism involving binding to synaptic vesicle protein 2A, inhibiting calcium release from intraneuronal stores, and modulating GABA and glycine-gated currents 2
• Dilantin (phenytoin) works primarily by blocking voltage-gated sodium channels 1

Pharmacokinetics

• Keppra is minimally protein-bound (<10%), has linear pharmacokinetics, and is primarily eliminated unchanged through the kidneys (66% of dose) 3
• Dilantin is highly protein-bound and has nonlinear pharmacokinetics with hepatic metabolism, making drug interactions more common 1

Drug Interactions

• Keppra has minimal drug interactions and does not induce cytochrome P450 enzymes 3, 2
• Dilantin is known to have numerous drug interactions due to its effect on liver enzymes 1, 4

Adverse Effects Profile

• Keppra's common side effects include nausea and rash; behavioral effects may include irritability and mood changes 1, 5
• Dilantin's adverse effects include soft tissue injury with extravasation, hypotension, cardiac dysrhythmias, and "purple glove syndrome" 1

Clinical Applications

Status Epilepticus Treatment

• Both medications can be used in status epilepticus, but with different dosing and considerations:
  • Keppra: 30-50 mg/kg IV at 100 mg/min 1
  • Dilantin: 18-20 mg/kg at a maximum rate of 50 mg/min 1

Efficacy in Refractory Seizures

• In studies of refractory status epilepticus, levetiracetam has shown efficacy rates of 67-73% 1
• The Veterans Affairs cooperative study showed only 56% success in terminating status epilepticus when diazepam was followed by phenytoin 1

Safety Considerations

• Keppra does not require therapeutic drug monitoring and has a more favorable safety profile in certain populations 6, 4
• Dilantin requires careful monitoring of drug levels and has more significant cardiovascular risks during administration 1

Special Populations

Brain Tumor Patients

• Levetiracetam is increasingly preferred in brain tumor patients due to:
  • Lack of enzyme induction that could affect chemotherapy 4
  • Potential to increase sensitivity of glioblastoma to temozolomide 4

Combination Therapy

• Levetiracetam shows enhanced protective activity when combined with other antiepileptic drugs, particularly with valproate, without exacerbating side effects 7
• This makes it valuable in polytherapy for drug-resistant patients 7

Important Clinical Pitfalls to Avoid

• Do not assume these medications are interchangeable - switching between them requires careful consideration of their different pharmacokinetics and side effect profiles 1
• Be aware that Keppra may cause behavioral side effects in some patients, ranging from mild (irritability, anxiety) to severe (psychosis, rarely catatonia) 5
• When administering IV Dilantin, monitor closely for cardiovascular complications and extravasation injuries that are not concerns with Keppra 1

Understanding these differences is crucial for appropriate medication selection and patient safety in seizure management.