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Phenytoin

Phenytoin is an anti-seizure medicine used to treat tonic-clonic (grand mal) seizures, complex partial (temporal lobe) seizures, and seizures during or after neurosurgery, and the injection is used for status epilepticus.

Brand names DilantinPhenytekPhenytoin InfatabsDilantin InfatabsDilantin-125
Drug class Anti-epileptic Agent
Rx Forms 5
Dr. Brian Staiger, PharmD, BCPS
Reviewed by Last reviewed Jul 10, 2026 Content updated Oct 2, 2026
🧬 Where this information comes from Click to expand

The clinical label records used on this page are FDA-filed Structured Product Labeling (SPL) retrieved through openFDA. We identified 40 clinical label sets within the page’s selected clinical scope after exact ingredient or ingredient-combination matching and applicable route/form matching. Forms, routes, brands, labelers, strengths, and NDC product-record counts are built separately from matching FDA National Drug Code Directory records. The linked DailyMed document is a representative official source for verification, not the page’s only clinical source. View the linked label on DailyMed →

✓No current FDA shortage listed · checked Oct 5, 2026
Other forms & routes:
Injection
Phenytoin at a glance The quick version — the full detail is in the Patient Information Guide below.
Dr. Brian Staiger, PharmD, BCPS
The Pharmacist’s Take By · Clinical pharmacist · Written

Phenytoin is an older standby seizure medicine, in use since about 1953 and available as a generic, for tonic-clonic (grand mal) and complex partial seizures, with an injection for status epilepticus (a prolonged seizure emergency); it is thought to calm misfiring nerve cells by blocking their sodium channels. Most people manage it, but sleepiness, dizziness, unsteadiness and jerky eye movements are common, especially when blood levels run high. Get help right away for a rash, blistering, mouth sores, or fever with swollen glands, which can signal a severe skin or allergic reaction. Never stop it suddenly, and expect blood tests, since a small dose change can raise levels sharply.

Clinical pearls

  • Take antacids at a different time of day from phenytoin, since taking them together can lower its levels.
  • Phenytoin can make oral contraceptives, apixaban, rivaroxaban and some statins less effective, so tell every prescriber you take it.
  • Chronic heavy drinking can lower phenytoin levels and a single bout of drinking can raise them, unsettling seizure control.
  • Chewable tablets and the oral suspension are not for once-daily dosing, and the suspension needs a proper measuring device.
How we write & review this content — our editorial policy →
How you get itPrescription only
Comes asExtended-release capsule, Injection, Chewable tablet +2
Earliest FDA record1953
Companies listing it with the FDA29
FDA label last updatedDec 24, 2024
FDA’s strongest warning (boxed)None on the label

Patient information guide A plain-language walkthrough of Phenytoin, written from its FDA label.

What Phenytoin is used for

▾

Phenytoin treats several seizure types, depending on the product.

  • Oral phenytoin products: tonic-clonic (grand mal) seizures and psychomotor (temporal lobe) or complex partial seizures.
  • Most oral capsules and chewable tablets, including Dilantin Infatabs and Phenytek: seizures during or following neurosurgery.
  • Dilantin-125 and Phenytoin oral suspension: tonic-clonic and psychomotor seizures.
  • Phenytoin Sodium Injection: generalized tonic-clonic status epilepticus and seizures during neurosurgery.
  • Intravenous Phenytoin Sodium Injection: short-term substitute for oral phenytoin when oral use is not possible.

How Phenytoin works

▾

The exact mechanism is not established. Phenytoin is thought to block voltage-dependent sodium channels on nerve cell membranes. This reduces sustained, high-frequency nerve firing, which helps prevent seizures from spreading.

Phenytoin dosage

▾

Oral phenytoin is taken by mouth, generally in divided doses through the day. Some extended-release capsules may be switched to once daily if your prescriber decides it is appropriate. Chewable tablets and suspension are not for once-daily use.

  • Chewable tablets (Dilantin Infatabs) can be chewed thoroughly or swallowed whole.
  • Measure suspension with a calibrated device.
  • The injection is given by healthcare professionals, usually by vein.
  • Follow your prescriber and label for dose and missed-dose directions.

Dosing details from the FDA-approved label

From the Phenytoin prescribing information (“Dosage and Administration”). Doses are set by your prescriber for your product, condition, kidney function and age — never change a dose on your own.

  • Status epilepticus – adults (injection)
    • Loading dose of 10 to 15 mg/kg administered slowly intravenously at a rate not exceeding 50 mg per minute
    • Followed by maintenance doses of 100 mg orally or intravenously every 6 to 8 hours
    • Maximum: Rate not exceeding 50 mg per minute
    • Continuous monitoring of ECG, blood pressure and respiratory function is essential
  • Status epilepticus – pediatric (injection)
    • Loading dose of 15 to 20 mg/kg intravenously, injected slowly at a rate not exceeding 1 to 3 mg/kg/min or 50 mg per minute, whichever is slower
    • Maximum: Rate not exceeding 1 to 3 mg/kg/min or 50 mg per minute, whichever is slower
    • Continuous monitoring of ECG and blood pressure is essential
  • Non-emergent loading dose – adults (injection)
    • Loading dose of 10 to 15 mg/kg administered slowly, followed by maintenance doses of oral or intravenous phenytoin every 6 to 8 hours
    • Maximum: Rate not exceeding 50 mg per minute
    • Oral phenytoin should be used whenever possible; slower administration rates are recommended to minimize cardiovascular adverse reactions
  • Non-emergent loading dose – pediatric (injection)
    • Administered intravenously at a rate not exceeding 1 to 3 mg/kg/min (or 50 mg per minute, whichever is slower)
    • Maximum: 1 to 3 mg/kg/min or 50 mg per minute, whichever is slower
    • Oral phenytoin should be used whenever possible
  • Adults with no previous treatment – divided daily dosage (extended capsules)
    • One 100-mg extended phenytoin sodium capsule by mouth three times daily
    • For most adults the satisfactory maintenance dosage is one capsule three to four times a day
    • Maximum: Up to two capsules three times a day
    • Adjust the dosage to suit individual requirements
  • Adults – once-a-day dosage (extended capsules)
    • If seizure control is established with divided doses of three 100-mg extended phenytoin sodium capsules daily, once-a-day dosage with 300 mg of extended phenytoin sodium capsules may be considered
    • Only extended phenytoin sodium capsules are recommended for once-a-day dosing
  • Pediatric patients (extended capsules)
    • Starting dose 5 mg/kg/day in two to three equally divided doses, with dosage adjustments as necessary
    • Maintenance dosage 4 mg/kg/day to 8 mg/kg/day
    • Maximum: 300 mg daily
Read the label’s full dosing text

2 DOSAGE AND ADMINISTRATION • Adult starting dose in patients who have received no previous treatment is one 100 mg extended phenytoin sodium capsule three times a day, with dose adjustments as necessary. For most adults, the satisfactory maintenance dose will be one capsule three to four times a day. An increase, up to two capsules three times a day may be made, if necessary. ( 2.1 ) • Adult once-a-day dose: If seizure control is established with divided doses of three 100 mg extended phenytoin sodium capsules daily, once-a-day dosage with 300 mg extended phenytoin sodium capsules may be considered. ( 2.1 ) • Adult loading dose: reserved for patients in a clinic or hospital setting who require rapid steady-state serum levels and where intravenous administration is not desired. Refer to full prescribing information. ( 2.1 ) • Pediatric starting dose is 5 mg/kg/day in two to three equally divided doses, with dosage adjustments as necessary, up to a maximum of 300 mg daily. Maintenance dosage is 4 mg/kg/day to 8 mg/kg/day. ( 2.2 ) • Serum blood level determinations may be necessary for optimal dosage adjustments—the clinically effective serum total concentration is 10 mcg/mL to 20 mcg/mL (unbound phenytoin concentration is 1 mcg/mL to 2 mcg/mL). ( 2.3 ) 2.1 Adult Dosage Divided daily dosage: The recommended starting dose for adult patients who have received no previous treatment is one 100-mg extended phenytoin sodium capsule by mouth three times daily. Adjust the dosage to suit individual requirements up to a maximum of two capsules three times a day. For most adults, the satisfactory maintenance dosage will be one capsule three to four times a day. Once-a-day dosage: In adults, if seizure control is established with divided doses of three 100-mg extended phenytoin sodium capsules daily, once-a-day dosage with 300 mg of extended phenytoin sodium capsules may be considered. Studies comparing divided doses of 300 mg with a single daily dose of this quantity indicated absorption, peak serum levels, biologic half-life, difference between peak and minimum values, and urinary recovery were equivalent. Once-a-day dosage offers a convenience to the individual patient or to nursing personnel for institutionalized patients and is intended to be used only for patients requiring this amount of drug daily.

Excerpted — the section continues on the label. Read the full Dosage and Administration section on DailyMed →

Phenytoin side effects

▾

Nervous system effects are the most common, and they are usually dose-related.

Common side effects

  • Nystagmus (involuntary eye movements)
  • Ataxia (unsteady walking or poor balance)
  • Slurred speech
  • Decreased coordination
  • Sleepiness
  • Mental confusion
  • Dizziness or headache
  • Nausea and vomiting
  • Gum overgrowth

When to get medical help

  • Get help right away for a rash, blistering or peeling skin, or mouth sores. These can be signs of severe skin reactions.
  • Call your doctor for fever, swollen glands, or facial swelling, with or without a rash. These can signal a serious allergic reaction (DRESS).
  • Seek emergency care for swelling of the face, lips or airway.
  • Report yellow skin or eyes, or signs of liver problems.
  • Report new or worsening depression, unusual mood or behavior changes, or thoughts of self-harm.
  • Seek help for a slow heartbeat or fainting. Slow heartbeat and cardiac arrest have been reported.
  • Tell your doctor about unusual bruising, bleeding, or frequent infections, which can signal blood count problems.
  • Do not stop suddenly. Abrupt withdrawal may trigger status epilepticus.

Phenytoin warnings and precautions

▾
  • Do not stop suddenly. Abrupt withdrawal may cause status epilepticus.
  • Severe skin reactions can be fatal. Stop at the first sign of a rash unless it is clearly not drug-related, and call your doctor.
  • DRESS (multiorgan hypersensitivity), angioedema and liver injury have been reported.
  • Slow heartbeat and cardiac arrest have been reported.
  • Blood count problems and swollen lymph nodes can occur.
  • Antiepileptic drugs can raise the risk of suicidal thoughts.
  • Long-term use is linked to weaker bones and low vitamin D.
  • Caution in porphyria.

Phenytoin interactions

▾

Phenytoin has many interactions because it is highly protein bound, has saturable metabolism, and strongly induces liver enzymes.

  • Delavirdine: must not be combined, since it can cause loss of HIV treatment response.
  • Antacids: can lower phenytoin absorption, so separate them.
  • Azole antifungals, certain antidepressants, cimetidine, omeprazole: may raise phenytoin levels.
  • Rifampin, carbamazepine, St. John's wort, chronic heavy alcohol use: may lower levels.
  • Warfarin, blood thinners like apixaban and rivaroxaban, oral contraceptives, statins: may be affected.
  • Valproate: risk of high ammonia.
  • Tube feeding: can lower phenytoin levels.

Interactions listed in the FDA-approved label

From the Phenytoin prescribing information (“Drug Interactions”): what the manufacturer studied or reported to the FDA.

  • Antiepileptic drugs (ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate): May increase phenytoin serum levels. Monitoring of phenytoin serum levels is recommended when a drug interaction is suspected; phenytoin dose adjustment may be required.
  • Azoles (fluconazole, ketoconazole, itraconazole, miconazole, voriconazole): May increase phenytoin serum levels; phenytoin also impairs the efficacy of azoles. Adjustment of the dose may be required when adding or withdrawing these agents.
  • Antacids (calcium carbonate, aluminum hydroxide, magnesium hydroxide): May decrease phenytoin serum levels and may affect absorption of phenytoin. Phenytoin and antacids should not be taken at the same time of day.
  • Valproate (valproate sodium, valproic acid): May either increase or decrease phenytoin serum levels; concomitant use has been associated with an increased risk of valproate-associated hyperammonemia. Patients treated concomitantly should be monitored for signs and symptoms of hyperammonemia.
  • Delavirdine: Phenytoin can substantially reduce the concentrations of delavirdine, which can lead to loss of virologic response and possible resistance. See Contraindications (4).
  • Neuromuscular blocking agents (cisatracurium, pancuronium, rocuronium, vecuronium): Resistance to the neuromuscular blocking action has occurred in patients chronically administered phenytoin. Monitor patients closely for more rapid recovery from neuromuscular blockade than expected; infusion rate requirements may be higher.
  • Warfarin: Increased and decreased PT/INR responses have been reported when phenytoin is coadministered with warfarin; warfarin may also increase phenytoin serum levels.
  • Anticoagulants (apixaban, dabigatran, edoxaban, rivaroxaban): Their levels are decreased by phenytoin.
  • Antiviral agents (fosamprenavir, nelfinavir, ritonavir): May decrease phenytoin serum levels; phenytoin with fosamprenavir alone may decrease the concentration of amprenavir.
  • Enteral feeding/nutritional preparations: Patients receiving them have lower than expected phenytoin serum levels. Phenytoin should not be administered concomitantly with an enteral feeding preparation; more frequent serum phenytoin level monitoring may be necessary.
Read the label’s full interactions text

7 DRUG INTERACTIONS Phenytoin is extensively bound to plasma proteins and is prone to competitive displacement. Phenytoin is primarily metabolized by the hepatic cytochrome P450 enzyme CYP2C9 and to a lesser extent by CYP2C19, and is particularly susceptible to inhibitory drug interactions because it is subject to saturable metabolism. Inhibition of metabolism may produce significant increases in circulating phenytoin concentrations and enhance the risk of drug toxicity. Monitoring of phenytoin serum levels is recommended when a drug interaction is suspected. Phenytoin is a potent inducer of hepatic drug-metabolizing enzymes. Multiple drug interactions because of extensive plasma protein binding, saturable metabolism and potent induction of hepatic enzymes. (7.1 , 7.2) 7.1 Drugs that Affect Phenytoin Concentrations Table 2 includes commonly occurring drug interactions that affect phenytoin concentrations. However, this list is not intended to be inclusive or comprehensive. Individual prescribing information from relevant drugs should be consulted. The addition or withdrawal of these agents in patients on phenytoin therapy may require an adjustment of the phenytoin dose to achieve optimal clinical outcome.

Excerpted — the section continues on the label. Read the full Drug Interactions section on DailyMed →

Not a complete list. The label covers the interactions the manufacturer studied or reported, and our own interaction database does not cover every medicine either. Bring your full medication list, including vitamins and herbal products, to your pharmacist.

🌿224 supplements and herbs with documented Phenytoin interactions, ranked by severity Check Phenytoin against a supplement or herb →

Before taking Phenytoin

▾
  • Allergy to phenytoin or other hydantoins is a contraindication.
  • Prior liver injury from phenytoin is a contraindication.
  • Pregnancy: risk of birth defects and fetal hydantoin syndrome. Newborns can have a bleeding disorder that may be prevented with vitamin K.
  • Breastfeeding: phenytoin passes into milk.
  • Older adults: may need lower or less frequent dosing.
  • Liver or kidney disease, or low albumin: unbound drug levels are monitored.
  • Decreased CYP2C9 function: may need lower doses.

Phenytoin overdose

▾

Too much phenytoin can cause nystagmus, unsteady walking, slurred speech, tremor, lethargy, blurred vision, nausea and vomiting. Severe cases can lead to coma, low blood pressure, slow heartbeat and cardiac arrest. There is no antidote, so treatment is supportive, and irreversible cerebellar damage has been reported.

How your body processes Phenytoin

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Phenytoin is mostly broken down by liver enzymes CYP2C9 and CYP2C19. This process can become saturated, so small dose increases may cause large jumps in blood levels. The average half-life is about 14 hours, and steady levels take at least 7 to 10 days. Chewable tablets peak at about 1.5 to 3 hours. Clearance is lower in older adults and can change during pregnancy.

How to store Phenytoin

▾

Store at 20° to 25°C (68° to 77°F) . Protect from moisture.

Written from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →

224

Supplements & herbs that interact with Phenytoin

224 supplements and herbal products have documented interactions with Phenytoin in the licensed clinical database we use. Most are manageable — but your pharmacist should know about everything you take, including vitamins and herbals.

Severity mix
  • Major · 9
  • Moderate · 187
  • Minor · 28
1,4-BUTANEDIOL Major ACTIVATED CHARCOAL Major BEER Major GAMMA-HYDROXYBUTYRATE (GHB) Major KAVA Major L-TRYPTOPHAN Major SIBERIAN COCKLEBUR Major ST. JOHN'S WORT Major +216 more
Every supplement checked against Phenytoin — ranked by severity The full interaction hub: 9 major · 187 moderate · 28 minor · every one linked to its full report. Check Phenytoin against your exact supplements

Educational information from a licensed clinical database (Natural Medicines) — see our data sources & update cadence. Not medical advice: an interaction being documented does not mean it will happen to you; do not start or stop medications or supplements without professional guidance.

13

Nutrient depletion considerations

Phenytoin has been associated with lower levels of 13 nutrients in the clinical literature. This does not mean a deficiency will occur — it means these may be worth discussing with your pharmacist or healthcare provider, especially with long-term use.

Evidence & significance mix
  • Higher significance · 5
  • Moderate · 7
  • Unrated · 1
ACETYL-L-CARNITINE Insignificant Depletion L-CARNITINE Insignificant Depletion PROPIONYL-L-CARNITINE Insignificant Depletion VITAMIN K Insignificant Depletion ZINC Insignificant Depletion BIOTIN Moderate Depletion CALCIUM Moderate Depletion FOLIC ACID Moderate Depletion +5 more
See the full Phenytoin nutrient depletion report

Educational information from a licensed clinical database (Natural Medicines) — not medical advice. Do not start or stop medications or supplements without professional guidance.

Phenytoin: pharmacist answers to common questions

Quick, plain-English answers to the questions patients ask most about Phenytoin — the kind of thing our pharmacy team would talk through with you at the counter.

What is phenytoin used for?

▾
It treats seizures. Depending on the product, that includes grand mal seizures, temporal lobe or complex partial seizures, and seizures during or after brain surgery. The injection treats status epilepticus, a prolonged seizure emergency.

Can I stop it if I feel fine?

▾
No. Stopping suddenly can trigger a dangerous, prolonged seizure. If you need to reduce or stop it, your prescriber will do it gradually.

What side effects should I expect?

▾
The most common are unsteadiness, eye movements, slurred speech, sleepiness and confusion. These are often dose-related, so tell your doctor if they appear. Call right away for a rash, swelling, fever with swollen glands, or yellow skin.

Do I need to watch other medicines I take?

▾
Yes. Phenytoin interacts with many drugs, including antacids, antifungals, warfarin, blood thinners and birth control. Tell me or your doctor about everything you take, including St. John's wort.

Is phenytoin safe in pregnancy?

▾
It can raise the risk of birth defects, so talk to your doctor right away if you are pregnant or planning to be. Do not stop it on your own, because seizures are also risky. A pregnancy registry is available.

Why might I need blood tests?

▾
Phenytoin levels can rise quickly with small dose changes or interactions. Blood tests help your prescriber find the right dose.

Is Phenytoin available over the counter?

▾
No. Phenytoin is a prescription medicine: every Phenytoin product listed with the FDA is prescription only, so it is not sold over the counter. Your prescriber decides whether it is appropriate for you, and your pharmacist dispenses it.

When was Phenytoin first available?

▾
The earliest FDA record we hold for Phenytoin is from 1953: its first approval in Drugs@FDA or its earliest product listing in the NDC Directory, whichever is older. Many older medicines were in use before their first formal FDA approval, so this is the earliest date on record, not necessarily when Phenytoin was first used.

Who makes Phenytoin?

▾
29 companies currently list Phenytoin products in the FDA's NDC Directory, including Sun Pharmaceutical Industries, Inc., Hikma Pharmaceuticals USA Inc., Remedyrepack Inc.. That count includes repackagers and distributors as well as manufacturers (companies that sell only the raw ingredient are not counted), so fewer companies actually make it; the label on your bottle names the one that supplied yours.

Answers drafted from the FDA-approved label with AI and reviewed by our pharmacy team. How we use AI →

More about Phenytoin on HelloPharmacist

📊Phenytoin supplement interactions224 checked — ranked by severity 🌿Drug & Supplement CheckerPhenytoin vs. vitamins & herbs 💬Ask a PharmacistFree answer, usually < 24h 🔎NDC & pricing lookupFind Phenytoin NDCs & costs 🅰️Browse Drugs A–ZLook up any medication
Detailed data & references for Phenytoin Forms & strengths, pricing, billing codes, manufacturers, safety reports and sourcing — the data behind the page. Most people can stop here. Each section below opens on a tap.

Phenytoin forms and strengths (how it comes)

Phenytoin is available in 5 forms. Different forms and brands can have different approved uses, doses, schedules, and directions. Follow the instructions for your exact product, and do not switch forms without guidance from your prescriber or pharmacist.

Need a version that does not list lactose, a gluten source, a dye or gelatin? Inactive ingredients differ by manufacturer: see Phenytoin inactive ingredients by manufacturer.

Extended-release capsule

By mouth
Brands Phenytek
How this form is used
What it may be used for
  • Phenytek capsules are used for tonic-clonic and psychomotor seizures and for seizures during or following neurosurgery.
Important instructions
  • Phenytek is usually started three times a day. Once-a-day dosing with the 300 mg capsule may be considered if seizures are controlled on divided doses.
  • Phenytek adult loading doses are reserved for clinic or hospital settings.
Available strengths 3 strengths
100 mg 200 mg 300 mg
31 FDA-listed product records ⓘ

Injection

Into a muscle · Into a vein
How this form is used
What it may be used for
  • Phenytoin Sodium Injection is used for generalized tonic-clonic status epilepticus and for seizures during neurosurgery.
  • Intravenous Phenytoin Sodium Injection can be substituted short-term for oral phenytoin.
Important instructions
  • Phenytoin Sodium Injection is given with continuous monitoring of heart rhythm, blood pressure and breathing.
  • Phenytoin Sodium Injection should ordinarily not be given into a muscle because of erratic absorption and local toxicity.
Available strengths 1 strength
50 mg/mL
25 FDA-listed product records ⓘ

Chewable tablet

By mouth
Brands Dilantin Infatabs Phenytoin Infatabs
How this form is used
What it may be used for
  • Dilantin Infatabs and Phenytoin Infatabs are used for generalized tonic-clonic and complex partial seizures and for seizures during or following neurosurgery.
Important instructions
  • Dilantin Infatabs are not for once-a-day dosing.
  • Dilantin Infatabs can be chewed thoroughly before swallowing or swallowed whole.
Available strengths 1 strength
50 mg
20 FDA-listed product records ⓘ

Capsule

By mouth
How this form is used
What it may be used for
  • Extended Phenytoin Sodium capsules are used for tonic-clonic and psychomotor seizures and for seizures during or following neurosurgery.
Important instructions
  • Extended Phenytoin Sodium capsules are usually started three times a day, per the label.
  • When switching between phenytoin products or between free acid and sodium salt forms, your doctor may check blood levels because drug content differs.
Available strengths 1 strength
100 mg
15 FDA-listed product records ⓘ

Oral suspension

By mouth
Brands Dilantin-125
How this form is used
What it may be used for
  • Dilantin-125 is used for tonic-clonic and psychomotor seizures.
Important instructions
  • Dilantin-125 is for oral use only, not for injection.
  • Dilantin-125 should be measured with a calibrated device, not a household spoon.
Available strengths 1 strength
125 mg/5 mL
11 FDA-listed product records ⓘ

Phenytoin on the U.S. market: products, makers and brands

How Phenytoin appears in the FDA’s National Drug Code Directory — including its dosage forms, strengths, brand names, manufacturers, and FDA-listed product records. These are directory records, not sales or prescription volume.

29 companies list 49 Phenytoin product records with the FDA, mostly as extended-release capsule, injection, chewable tablet; the earliest marketing or approval year on record is 1953. Brand names on the directory include Dilantin, Phenytek, Phenytoin Infatabs and 2 more; the rest are generics.

5
Dose forms ⓘ
29
Labelers (makers, repackagers, distributors)
7
Brand names
49
FDA-listed product records ⓘ
1953
Earliest FDA record ⓘ

FDA-listed product records by dose form (tablet variants merged) — FDA National Drug Code Directory. Record counts are not sales or prescription volume.

Also listed with the FDA, not a patient dose form: Powder (18) — bulk drug substance sold to compounders/manufacturers and multi-item kits. These aren’t counted in the dose-form total above.

Sun Pharmaceutical Industries, Inc.10%
Hikma Pharmaceuticals USA Inc.8%
Remedyrepack Inc.8%
American Health Packaging6%
NCS HealthCare of KY, LLC dba Vangard Labs6%
A-S Medication Solutions4%
Other makers57%

Share of FDA-listed product records by manufacturer — FDA National Drug Code Directory. Record counts are not sales or prescription volume.

How widely Phenytoin is used (Medicaid data)

A general measure of how commonly Phenytoin is prescribed, based on Medicaid — one of the largest public drug programs. The figure below is prescriptions filled in Q1–Q4 2025, summed across every form and brand of the drug.

Think of this as a proxy for how widely Phenytoin is used, drawn from freely available public data. Medicaid is just one program — these numbers don’t include Medicare, other government coverage, or commercial and cash-pay prescriptions, so real-world use is higher than what’s shown here.

189,728
Medicaid prescriptions filled (Q1–Q4 2025)
$7.8M gross Medicaid reimbursement (before mandatory rebates — net cost is lower)

How commonly is Phenytoin prescribed? Of the 1,601 medications we measure, Phenytoin ranks #399 by Medicaid prescriptions — more than 75% of them.

Where Phenytoin ranks among the drugs we measure · Q1–Q4 2025 · neighbors ±5
Total prescriptions — #399 of 1,601
#394 Hydromorphone Injectio... 195,712 Rx #395 Chlorpromazine 195,153 Rx #396 Amlodipine and Benazep... 194,518 Rx #397 Ticagrelor 190,826 Rx #398 Atogepant 190,760 Rx #399 Phenytoin 189,728 Rx #400 Triamterene and Hydroc... 189,372 Rx #401 Pramipexole 188,853 Rx #402 Ciprofloxacin Ophthalm... 187,373 Rx #403 Esketamine Nasal Spray 184,743 Rx #404 Benazepril 184,412 Rx

Utilization by Phenytoin product

Pick a product to see its own Medicaid numbers. Each chip is one clinical product — a specific strength & dosage form as defined by RxNorm — with brand-name and generic versions combined.

The 100 mg extended release oral capsule is the most-dispensed Phenytoin product — about 84% of these Medicaid prescriptions.

phenytoin sodium 100 MG Extended Release Oral Capsule Most dispensed

159,099 Medicaid prescriptions (Q1–Q4 2025) 84% of Phenytoin prescriptions shown $6.1M gross reimbursement (before rebates) ≈ $39 per prescription (gross)

Summed across the 9 of 137 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 855671

phenytoin 50 MG Chewable Tablet

17,486 Medicaid prescriptions (Q1–Q4 2025) 9% of Phenytoin prescriptions shown $792,438 gross reimbursement (before rebates) ≈ $45 per prescription (gross)

Summed across the 4 of 24 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 1313885

phenytoin 25 MG/ML Oral Suspension

6,283 Medicaid prescriptions (Q1–Q4 2025) 3% of Phenytoin prescriptions shown $181,254 gross reimbursement (before rebates) ≈ $29 per prescription (gross)

Summed across the 5 of 20 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 1313112

phenytoin sodium 30 MG Extended Release Oral Capsule

3,236 Medicaid prescriptions (Q1–Q4 2025) 2% of Phenytoin prescriptions shown $415,823 gross reimbursement (before rebates) ≈ $128 per prescription (gross)

Summed across the 1 of 5 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 855869

phenytoin sodium 300 MG Extended Release Oral Capsule

1,929 Medicaid prescriptions (Q1–Q4 2025) 1% of Phenytoin prescriptions shown $167,473 gross reimbursement (before rebates) ≈ $87 per prescription (gross)

Summed across the 2 of 6 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 855873

phenytoin sodium 200 MG Extended Release Oral Capsule

1,682 Medicaid prescriptions (Q1–Q4 2025) <1% of Phenytoin prescriptions shown $131,547 gross reimbursement (before rebates) ≈ $78 per prescription (gross)

Summed across the 3 of 7 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 855861

5 ML phenytoin sodium 50 MG/ML Injection

13 Medicaid prescriptions (Q1–Q4 2025) <1% of Phenytoin prescriptions shown $543 gross reimbursement (before rebates) ≈ $42 per prescription (gross)

Summed across the 1 of 10 listed NDC products with Medicaid activity — every brand and generic of this exact strength & form. RxNorm 1670353

Shares are of the Medicaid prescriptions shown here. Product grouping follows RxNorm (the National Library of Medicine’s drug terminology), so “one product” means one strength & dosage form regardless of manufacturer. Dollar figures are gross Medicaid reimbursement before mandatory rebates — rebates (often large, especially for brand-name drugs) are confidential, so actual net cost to Medicaid is lower than shown.

Source: Medicaid State Drug Utilization Data (CMS), aggregated by generic ingredient — summed across every NDC (all brands, strengths, salt forms and dosage forms) of Phenytoin, and across all states and both fee-for-service and managed-care claims. A general popularity signal; it excludes Medicare, commercial insurance and cash prescriptions, so it is not total U.S. use. Based on the 25 of 209 listed Phenytoin NDCs with Medicaid activity.

Compare Phenytoin products

A representative set of FDA-listed product records for Phenytoin — across manufacturers, strengths, and dosage forms, grouped by form with each product’s manufacturer and how the FDA approved it. The same medicine may be made and packaged by different companies, so a single drug can have many directory entries. (It’s also why a refill can look different — a new shape, color, or box — even though it contains the same medication.)

Showing 49 of 49 products — FDA National Drug Code Directory. See every product, package size and price: browse all 49 Phenytoin NDCs →

Phenytoin recall history

A recall is when a specific batch of a medicine is pulled from the market — usually a manufacturing issue, not a problem with the drug itself. Class I is most serious, Class III least.

The FDA’s enforcement reports list 3 Phenytoin recalls since July 2021, covering 4 product listings. None of them is still listed as ongoing. A recall names specific lots from one company, so check the lot number on your own bottle rather than assuming every product is affected; your pharmacist can check whether your supply came from an affected lot.

Class II Oct 27, 2023 · Terminated · Amneal Pharmaceuticals of New York, LLC
Failed Dissolution Specifications
  • Extended Phenytoin Sodium Capsules, USP, 100 mg, 100-count bottle, Distributed by Amneal Pharmaceuticals LLC Bridgewater, NJ, 08807, NDC# 65162-212-10 Lots: Lot # HM03221A, Exp. date 12/31/2023 FDA record D-0090-2024 →
Class II May 30, 2023 · Terminated · Amneal Pharmaceuticals of New York, LLC
Failed Dissolution Specifications: Out-of-specification results for dissolution (above specification)
  • Extended Phenytoin Sodium Capsules, USP, 100 mg, Rx Only, 100 capsules per bottle, Distributed by: Amneal Pharmaceuticals LLC., Bridgewater, NJ 08807, NDC 65162-212-10. Lots: Lot # HL00721A, Exp. 12/2023 FDA record D-0876-2023 →
Class III Nov 14, 2022 · Terminated · Acella Pharmaceuticals, LLC
Labeling: Not elsewhere classified; the product is being recalled because of customer complaints that the primary vial label was missing a barcode.
  • Phenytoin Sodium Injection, USP, 250 mg/5 mL, NDC 42192-614-05, packaged in 10 x 5 mL vials per carton, NDC 42192-614-30, Rx only, Manufactured for: Acella Pharmaceuticals, LLC Alpharetta, GA 30005 Lots: Lot: E026A001 Exp. 06/2023 FDA record D-0070-2023 →
  • Phenytoin Sodium Injection, USP 100 mg/2 mL, NDC 42192-614-02, packaged in 10 x 2 mL vials per carton, NDC 42192-614-10, Rx only, Manufactured for: Acella Pharmaceuticals, LLC Alpharetta, GA 30005 Lots: Lot: E025A001 Exp. 07/2023 FDA record D-0069-2023 →

Source: FDA enforcement (recall) reports, via openFDA; our copy was last updated Sep 24, 2026.

RxNorm Concept Web — From Ingredient to Every Form and Strength

This page starts with one ingredient concept (IN). The branches below show its dose-form concepts (SCDF), then the available clinical drug and strength concepts (SCD). Combination products remain separate concepts with their own pages.

Ingredient (IN) Phenytoin RxCUI 8183 7 dose forms · 16 strengths
  1. Dose form (SCDF) Cartridge RxCUI 1670368 No current FDA listing
    Clinical drug / strength (SCD) 2 ML phenytoin sodium 50 MG/ML RxCUI 855911
  2. Dose form (SCDF) Chewable Tablet RxCUI 373433 In current FDA listings
    Clinical drug / strength (SCD) 50 MG RxCUI 1313885
  5. Dose form (SCDF) Oral Capsule RxCUI 373434 In current FDA listings
    Clinical drug / strength (SCD) sodium 100 MG RxCUI 855675 sodium 25 MG RxCUI 855936 sodium 300 MG RxCUI 855945 sodium 50 MG RxCUI 855946
  6. Dose form (SCDF) Oral Suspension RxCUI 373438 In current FDA listings
    Clinical drug / strength (SCD) 6 MG/ML RxCUI 1313888 18 MG/ML RxCUI 1313890 25 MG/ML RxCUI 1313112
  7. Dose form (SCDF) Oral Tablet RxCUI 373432 No current FDA listing
    Clinical drug / strength (SCD) sodium 100 MG RxCUI 855930

Look up RxCUI 8183 in the RxCUI Atlas →

RxNorm is the U.S. National Library of Medicine’s normalized drug vocabulary. Its concept hierarchy can include forms that are not currently marketed; the status on each branch compares that concept with current FDA listings. RxCUIs identify vocabulary concepts, not individual packages or manufacturers.

💵 What Phenytoin costs pharmacies (NADAC benchmark)

The national average invoice price pharmacies pay for the drug itself, from CMS's NADAC survey (data as of Sep 30, 2026). This is a supply-cost benchmark — not a retail price and not what you'd pay at the counter.

FormStrengthPharmacy acquisition benchmark
Capsule, Extended Release · Oral 100 mg $0.145 per capsule NDC details & price history
Capsule, Extended Release · Oral 300 mg $2.10 per capsule NDC details & price history
Capsule, Extended Release · Oral 200 mg $0.989 per capsule NDC details & price history
Tablet, Chewable · Oral 50 mg $1.57–$1.58 per tablet NDC details & price history
Why show this? Your out-of-pocket cost depends on insurance, pharmacy markup, and discounts — but the acquisition benchmark tells you whether the medication itself is inexpensive or costly, which strengths cost more per dose, and whether a cash-price quote is in a reasonable range. Each row links to the NDC-level record with its full price history.

Source: CMS National Average Drug Acquisition Cost (NADAC), a survey of retail pharmacy invoice prices. Benchmarks shown are the range across package sizes of a representative product for each form and strength — other manufacturers' products may differ.

Phenytoin brand names

Phenytoin is sold under 5 brand names in the FDA directory — Dilantin, Phenytek, Phenytoin Infatabs, Dilantin Infatabs and others. A brand and its generic contain the same active ingredient; the brand name belongs to one company's product.

Dilantin Phenytek Phenytoin Infatabs Dilantin Infatabs Dilantin-125

Who makes Phenytoin: manufacturers and labelers

29 companies list Phenytoin products with the FDA. By number of product records, the largest are Sun Pharmaceutical Industries, Inc., Hikma Pharmaceuticals USA Inc., Remedyrepack Inc.. Labelers include manufacturers and repackagers; the product in your bottle depends on which one your pharmacy stocks.

Sun Pharmaceutical Industries, Inc. 5 Hikma Pharmaceuticals USA Inc. 4 Remedyrepack Inc. 4 American Health Packaging 3 NCS HealthCare of KY, LLC dba Vangard Labs 3 A-S Medication Solutions 2 Aphena Pharma Solutions - Tennessee, LLC 2 HF Acquisition Co LLC, DBA HealthFirst 2 Henry Schein, Inc. 2 Major Pharmaceuticals 2 Mylan Pharmaceuticals Inc. 2 Atlantic Biologicals Corp. 1 Acella Pharmaceuticals, LLC 1 Amneal Pharmaceuticals LLC 1 Aurobindo Pharma Limited 1 AvPAK 1 Bryant Ranch Prepack 1 Coupler LLC 1 Direct Rx 1 Golden State Medical Supply, Inc. 1 Medical Purchasing Solutions, LLC 1 PAI Holdings, LLC dba PAI Pharma 1 Parke-Davis Div of Pfizer Inc 1 Prasco Laboratories 1

…and 5 more on the FDA NDC directory.

Phenytoin drug class (RxNorm)

Phenytoin belongs to the Anti-epileptic Agent class.

Pharmacologic class Anti-epileptic Agent
Drug family (ATC) Hydantoin derivatives
How it works Cytochrome P450 2C9 Inducers, Cytochrome P450 2C19 Inducers, Cytochrome P450 2C8 Inducers, Cytochrome P450 2B6 Inducers

Classified by RxNorm RxClass — the U.S. National Library of Medicine's standardized drug-classification service (Established Pharmacologic Class from the FDA, the ATC drug family from the WHO, and mechanism of action). Reference only, not medical advice.

Sources for this Phenytoin page

Core label, product, RxNorm, safety, and utilization data on this page come from the sources identified below. AI-written, editorial, and licensed sections are labeled separately.

📄
FDA-filed drug labels (SPL) Uses, dosing, warnings & side effects from SPL records retrieved through openFDA; the linked representative set can be verified on DailyMed. ✓ Linked label effective Dec 24, 2024
🏭
Forms, brands & labelersAggregated from ingredient-matched FDA National Drug Code Directory product records for Phenytoin.
📈
Real-world reportsThe FDA Adverse Event Reporting System (FAERS), served through openFDA.
🚨
Recalls & shortagesopenFDA drug-enforcement reports and the FDA drug-shortage database.
🧾 Clinical label set — FDA-filed SPL labels retained for Phenytoin after exact ingredient or ingredient-combination matching and applicable route/form matching
Clinical labels in scope
40
Finished products in the current FDA directory
49
Companies listing them (makers, repackagers, distributors)
29
FDA labeler codes behind them ⓘ
31
Linked representative label ⓘ
Greenstone LLC
Linked label effective
Dec 24, 2024
Composite sections available
22
Linked SPL Set ID
37943ec1-a8d2-42df-967e-6f96f84c017b
Linked SPL Document ID
212141a3-fffd-49e0-96d5-57cc921a99d1
Open the linked representative label on DailyMed ↗

How this page is built

HelloPharmacist combines public FDA and NLM records and does not author the underlying clinical facts. The plain-language sections are written with AI from the FDA-approved label text and reviewed by our pharmacy team before publication. Greenstone LLC is the representative DailyMed label linked for verification and dates. This is general education, not medical advice: always talk to your doctor or pharmacist about your own medicines. How we build and review drug pages →