Dilantin (phenytoin) vs Keppra (levetiracetam)
Both drugs are antiepileptic medications, but they work very differently, have distinct side‑effect profiles, and are used in slightly different clinical situations. Below is a side‑by‑side comparison to help you decide which might be right for you (or your loved one) – but remember: only a qualified health professional can make the final call.
| Feature | Dilantin (phenytoin) | Keppra (levetiracetam) |
|---------|----------------------|------------------------|
| Drug class | Sodium‑channel blocker | Synaptic vesicle protein‑2A (SV2A) modulator |
| Mechanism | Stabilizes neuronal membranes by blocking voltage‑gated sodium channels, especially in the refractory phase of the action potential. | Binds to SV2A protein on presynaptic terminals, reducing excitatory neurotransmitter release; exact mechanism still being studied. |
| Typical uses | • Partial‑onset seizures (with or without secondary generalization)
• Generalized tonic‑clonic seizures
• Post‑traumatic seizures (short‑term)
• Status epilepticus (often first line) | • Partial‑onset seizures
• Generalized tonic‑clonic seizures (when used with other agents)
• Lennox‑Gastaut syndrome (often as add‑on)
• Myoclonic seizures (in combination therapy) |
| Dosage (adult) | 300–600 mg/day divided in 2–3 doses; titrate to serum 10–20 µg/mL (therapeutic range). | 500–1,000 mg twice daily (1–4 g/day), titrate based on response. |
| Monitoring | • Serum phenytoin level (to avoid toxicity).
• Liver function tests; CBC; blood pressure. | • Generally no routine labs.
• Monitor for behavioral changes. |
| Common side effects | • Cognitive/behavioral: confusion, difficulty concentrating, memory problems.
• Neuromuscular: ataxia, dysarthria, slurred speech.
• Dermatologic: rash (rarely Stevens–Johnson), gingival hyperplasia, hirsutism.
• Gastrointestinal: nausea, vomiting.
• Metabolic: hypocalcemia, hypomagnesemia. | • Neuropsychiatric: irritability, depression, anxiety, aggression, insomnia, mood swings.
• Gastrointestinal: nausea, vomiting, anorexia.
• Other: mild dizziness, headache. |
| Serious but rare | • SJS/TEN (rash, mucosal ulceration).
• Hepatotoxicity (especially in young patients).
• Drug‑induced gingival hyperplasia. | • Severe psychiatric reactions (rare).
• Serotonin syndrome (when combined with SSRIs). |
| Drug interactions | • Strongly induces CYP450 enzymes (especially CYP2C9, CYP2C19) → lowers levels of many drugs (oral contraceptives, warfarin, carbamazepine, etc.).
• Metabolized by CYP2C9 (genetic polymorphisms matter). | • Minimal CYP interaction; mostly excreted unchanged by the kidneys.
• Can increase serum levels of valproate (increases risk of valproate toxicity). |
| Contraindications | • Known hypersensitivity to phenytoin.
• Severe hepatic impairment.
• Pregnancy (category C – risk of fetal myelodysplasia). | • Known hypersensitivity to levetiracetam.
• Severe renal impairment (dose adjustment needed). |
| Pregnancy & Lactation | • Category C: may harm fetus; use only if benefits outweigh risks.
• Secreted into breast milk – caution. | • Category B: no proven risk in animal studies.
• Limited data in pregnancy; generally considered safe if needed.
• Excreted into breast milk – generally considered low risk. |
| Cost & Accessibility | Older, generic drug → usually inexpensive. | Brand‑name drug (though generics available). Usually pricier, but often covered by insurance. |
| When you might choose each | • When you need rapid seizure control (e.g., status epilepticus).
• When you’re already on a drug that interacts favorably (e.g., carbamazepine).
• When cost is a major consideration. | • When the patient has a history of drug‑resistant seizures that responded to levetiracetam.
• When you want a medication with fewer drug‑drug interactions and minimal hepatic metabolism.
• When you want to avoid the cognitive side‑effects of phenytoin. |
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Practical take‑aways
| Scenario | Likely Choice | Why |
|--------------|-------------------|---------|
| First‑line for acute seizure (status epilepticus) | Dilantin | Fast onset, well‑established in emergency settings. |
| Long‑term management of partial seizures with minimal cognitive impact | Keppra | Better neurocognitive profile, easy once‑daily dosing. |
| Patient on multiple CYP‑inducing drugs | Keppra | Avoids the enzyme‑inducing effect of phenytoin. |
| Budget‑conscious, generic‑only regimen | Dilantin | Cheaper generic formulation. |
| Pregnant woman needing seizure control | Keppra (with close monitoring) | Generally considered safer, but discuss with OB‑neuro specialist. |
| Patient with hepatic dysfunction | Keppra | Avoids hepatic metabolism and potential hepatotoxicity. |
| Patient who previously had a rash with a different antiepileptic | Dilantin (if not rash‑susceptible) | But be vigilant; any rash may be a sign of severe reaction. |
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Quick FAQ
| Question | Short answer |
|----------|--------------|
| Can I switch from Dilantin to Keppra? | Yes, but taper off phenytoin slowly to avoid breakthrough seizures and monitor for withdrawal. |
| What are the most dangerous side effects of each? | Dilantin: rash (SJS/TEN), ataxia, gingival hyperplasia, hypocalcemia.
Keppra: severe psychiatric reactions (rare), serotonin syndrome if combined with SSRIs. |
| Which drug is easier to dose? | Keppra is usually just twice daily (1–2 g/day). Dilantin requires careful titration to serum levels. |
| Do I need blood tests for Keppra? | Routine labs are usually unnecessary. |
| Is phenytoin safe during pregnancy? | Category C – use only if benefits > risks. |
| Can Keppra be taken with other AEDs? | Yes, commonly used as add‑on. Check for valproate interaction. |
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Bottom line
- Dilantin (phenytoin): powerful, older drug, great for acute seizure control but requires blood‑level monitoring and has a higher chance of cognitive or dermatologic side effects.
- Keppra (levetiracetam): newer, simpler dosing, fewer drug interactions, but watch out for mood changes and occasional insomnia.
Choosing between them depends on seizure type, comorbid conditions, existing meds, pregnancy status, cost, and individual tolerance to side effects. Always discuss with your neurologist or prescriber—they’ll consider your full medical history and possibly do some lab monitoring to make the best choice.