Eptoin (Phenytoin Sodium)
Also sold as: Eptoin, Dilantin, Phenytoin, Phenytek, Fenitoina
Pregnancy
Cat D
Lactation
Caution
Schedule
H
Forms
Tablet 50mg, 100mg +3
Indications
- Tonic-clonic (grand mal) seizures
- Complex partial seizures
- Status epilepticus (IV — after benzodiazepines)
- Seizure prophylaxis post-neurosurgery / head trauma
- Trigeminal neuralgia (off-label)
Adult Dosing
Epilepsy (maintenance)
300-400 mg/day PO in 1-2 divided doses
Start 100 mg TDS; titrate over weeks. Narrow therapeutic index — TDM essential
Status epilepticus (IV)
15-20 mg/kg IV loading at max 50 mg/min (in NS — NOT dextrose)
MUST monitor ECG and BP during IV infusion. Followed by 100 mg IV every 6-8 hours maintenance.
Post-neurosurgery prophylaxis
100 mg PO/IV TDS
7 days or per neurologist guidance
Pediatric Dosing
Neonates: 15-20 mg/kg loading IV; maintenance 5 mg/kg/day. TDM mandatory in all paediatric patients.
Renal Dose Adjustment
| CrCl / eGFR | Dose Adjustment |
|---|---|
| CKD | Protein binding altered — measure free phenytoin levels (not total) in hypoalbuminaemia or renal failure. Total level underestimates active drug. |
Hepatic Adjustment
Reduce dose in hepatic impairment — phenytoin highly hepatically metabolised (CYP2C9)
Pregnancy & Lactation
Pregnancy: Category D
TERATOGENIC — fetal hydantoin syndrome (cleft palate, cardiac defects, digit anomalies, growth restriction, neurodevelopmental delay). Supplement folic acid 5 mg/day pre-conception and throughout pregnancy. Use only when benefit outweighs risk; prefer safer alternatives (lamotrigine, levetiracetam).
Lactation: Caution
Excreted in breast milk; sedation reported in infants. Monitor infant for drowsiness.
Top Drug Interactions
| Interacting Drug | Effect | Severity |
|---|---|---|
| Warfarin | Complex bidirectional: initially increases then decreases anticoagulation — frequent INR monitoring | Major |
| Oral contraceptives | Phenytoin induces CYP3A4 — significantly reduces OCP efficacy; use alternative contraception | Major |
| Azole antifungals (fluconazole, voriconazole) | Significantly increases phenytoin levels — toxicity risk | Major |
| Carbamazepine / Rifampicin / Phenobarbitone | Reduce phenytoin levels (enzyme induction) | Major |
| Valproate | Displaces phenytoin from protein binding — free level rises even if total looks normal | Major |
| Antacids, tube feeds | Reduce phenytoin absorption — separate by 2-3 hours | Moderate |
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Side Effects
Common
- Nystagmus (first sign of toxicity)
- Ataxia
- Diplopia
- Drowsiness
- Gingival hyperplasia (cosmetically significant)
- Hirsutism
- Coarse facial features
- Peripheral neuropathy (long-term)
Serious / Discontinue If
- Phenytoin toxicity: nystagmus → ataxia → mental status changes → coma (levels > 40 mg/L)
- Stevens-Johnson syndrome / TEN
- Purple glove syndrome (IV extravasation)
- Cardiac arrhythmia / hypotension (rapid IV infusion)
- Hepatotoxicity, folic acid deficiency, osteomalacia (long-term)
Contraindications
- Sinus bradycardia, SA block, 2nd/3rd degree AV block (IV phenytoin)
- Adams-Stokes syndrome
- Concurrent delavirdine use
Available Indian Brands
| Brand | Manufacturer | Price (approx) |
|---|---|---|
| Eptoin 100mg | Abbott | 100 tab ₹65 |
| Eptoin 50mg (Infatabs) | Abbott | 50 tab ₹52 |
| Phenytoin Injection 250mg | Neon Labs | Amp ₹28 |
Monitoring Required
- Serum phenytoin level: Total therapeutic: 10-20 mg/L; Free therapeutic: 1-2.5 mg/L
- Draw trough sample (before next dose)
- CBC, LFTs (annually)
- Folic acid levels (megaloblastic anaemia risk)
- Bone mineral density (long-term)
- ECG and BP during IV loading
- Dental hygiene (gingival hyperplasia)
Patient Counseling Points
- Take at the same time every day — consistency is crucial (narrow therapeutic index)
- Do NOT stop suddenly — risk of status epilepticus
- Avoid alcohol — increases CNS toxicity
- Women on OCP: use additional contraception method
- Report: increasing dizziness, slurred speech, rash — signs of toxicity
- Brush teeth and floss regularly — prevents gingival overgrowth
- Carry seizure identity card at all times
Stop Googling drug references mid-consultation
EasyClinic auto-flags Eptoin interactions, renal cutoffs, and pregnancy warnings the moment you write the prescription. Built-in safety net for every Indian doctor.
Clinically reviewed by: Dr. Vikram Sinha, DM (Neurology), Senior Neurologist
Last reviewed: 2026-04-01
References
- BNF — Phenytoin
- IAP Epilepsy Guidelines 2024
- ILAE Epilepsy Treatment Guidelines
- AAN Status Epilepticus Guidelines