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Phenytoin Sodium 100 mg Capsule, Extended Release — NDC 51672-4111-00 package photo

Phenytoin Sodium 100 mg Capsule, Extended Release

by Sun Pharmaceutical Industries, Inc. · 10 BLISTER PACK in 1 CARTON (51672-4111-0) / 10 CAPSULE, EXTENDED RELEASE in 1 BLISTER PACK
NDC 51672-4111-00
🏷️ FDA NDC (as labeled) 51672-4111-0 billing pads the package segment with a zero
This package
Contains10 capsule, extended release in 1 blister pack Pack sizes4 compare ↓
Also comes in: 30 capsules 51672-4111-06 100 capsules 51672-4111-01 1000 capsules 51672-4111-03
Rx only Generic Discontinued Non-controlled ⚠ Discontinued by firm
🗂️ Data synced Sep 17, 2026 · sources: openFDA · FDA label (DailyMed) · FDA Orange & Purple Book · First Databank · CMS NADAC, ASP, Medicare & Medicaid · RxNorm
📋 All sources & update times →

This page is curated, coded, and maintained by

Compiled from public FDA, CMS, DailyMed, NADAC, and related drug data sources. Editorial policy

⚠️
Excluded from the active FDA NDC Directory. The labeler reported this product as discontinued, so it is excluded from the active NDC Directory. A label may still appear on DailyMed, but the NDC is no longer in the current FDA NDC Directory. Search the FDA NDC Directory ↗

🆔 Identity & classification

FDA NDC (as labeled) 51672-4111-0
Product NDC 51672-4111
11-digit billing NDC 51672411100
RxCUI 855671
UNII 4182431BJH
UPC 0351672411114
Application # ANDA040684
SPL Set ID 601f7353-225d-4a5d-9810-3869c2c21874
Established class (EPC) Anti-epileptic Agent; Cytochrome
Mechanism of action Cytochrome P450 1A2 Inducers; Cytochrome P450 2B6 Inducers; Cytochrome P450 2C19 Inducers; Cytochrome P450 2C8 Inducers; Cytochrome P450 2C9 Inducers; Cytochrome P450 2D6 Inducers
DEA schedule Non-controlled
Marketing category ANDA
Marketing status Discontinued
FDA listing status Discontinued by firm
Marketing start 2006-09-05
Route ORAL
Dosage form CAPSULE, EXTENDED RELEASE
Substance PHENYTOIN SODIUM
GPI-14 72200030200110
GPI class Phenytoin Sodium Extended
TE code (Orange Book) AB · RLD · RS
Why two NDCs? The FDA registers this code as 51672-4111-0 — a 5-4-1 layout, and that's what's printed on the package and shown on DailyMed. For insurance claims, every NDC is standardized to a uniform 11-digit 5-4-2 format by adding a zero to the package segment → 51672-4111-00. Same drug, same package — only the format differs.
Where does this data come from?
Identifiers from the FDA openFDA NDC Directory and Structured Product Labeling; RxCUI from RxNorm (NLM); GPI from Medi-Span; GCN / HIC / AHFS / legend from First Databank.

🏷️ RxNorm drug class

This medicine 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
Where does this data come from?
Therapeutic classes from RxNorm RxClass (U.S. National Library of Medicine) — Established Pharmacologic Class (FDA), ATC drug family (WHO) and mechanism of action, matched by this product’s RxCUI.

🏭 Manufacturer & labeler

LabelerSun Pharmaceutical Industries, Inc.
Application holderTARO PHARMACEUTICAL INDUSTRIES LTD
FDA applicationANDA040684 (ANDA)
Labeler code51672
First marketedSep 2006
Product typeHuman Prescription Drug
Portfolio889 products on file
The labeler markets the product; the application holder owns the FDA approval. They’re often the same company but can differ (e.g. a repackager or an authorized generic). A mailing address / phone appears here when the manufacturer includes it in the product’s FDA label (not all do).
Where does this data come from?
Labeler, application holder and registered establishment from the FDA openFDA NDC Directory and Drugs@FDA; address/contact from the product’s FDA label.

🩺 Clinical

📗 Our plain-language guide HelloPharmacist
  • Phenytoin is an antiseizure medication — it's used to treat and prevent different types of seizures, including tonic-clonic (grand mal) seizures, complex partial seizures, and seiz...
  • The most important thing is to take it exactly as prescribed and not skip doses. If you're on chewable tablets or the liquid suspension, those are not once-a-day medications — they...
  • How do I take phenytoin correctly — are there any tricks I should know?
  • The most common side effects involve your nervous system — things like dizziness, unsteady walking, slurred speech, drowsiness, and rapid eye movements. These are often dose-relate...
📖 Read our full Phenytoin guide →

Supplement & herbal interactions

🌿 Drug–supplement interaction checker →
13
Nutrient depletion considerations

Phenytoin may be associated with lower levels of 13 nutrients — worth a chat with your pharmacist, not a cause for alarm.

🧪 Full Phenytoin nutrient depletion report →
An association is not a deficiency. Educational only — don't start or stop anything without professional guidance.
Where does this data come from?
Plain-language summary from MedlinePlus (U.S. National Library of Medicine); supplement & herbal interactions and nutrient depletion data from the Natural Medicines database; our full guide is HelloPharmacist editorial content.

💊 What it looks like

Color orange
ShapeCapsule
ImprintTARO;PHN;100
Size16 mm
ScoringNot scored
One label can cover several strengths, so colors may be combined — always confirm a loose pill against the dispensed prescription label or a pharmacist.
Where does this data come from?
Physical description (imprint, shape, color, scoring, coating) from this product’s FDA Structured Product Labeling (SPL), mirrored from DailyMed / openFDA.

🧪 Inactive Ingredients / Excipients

Inactive ingredients, also called excipients, are components of the drug product other than the active ingredient. They may include fillers, dyes, coatings, preservatives, flavors, or other formulation ingredients.

💡 Tap an ingredient (hover on desktop) to see what it is and why it’s used.

  • UNII LKG8494WBH
    Benzyl alcohol is a clear liquid used as a preservative and solvent in medicines. It helps prevent bacterial and fungal growth and dissolves other ingredients to create uniform liquid formulations.
  • UNII 3QPI1U3FV8
    A preservative derived from benzoic acid that prevents bacterial and fungal growth in medicines. It helps extend shelf life and maintain product safety during storage and use.
  • UNII 35SW5USQ3G
    A synthetic yellow dye used to color medicines. It helps make tablets, capsules, and liquids visually distinct so patients can easily identify their medication.
  • UNII 25IH6R4SGF
    Edetate calcium disodium is a chelating agent, a chemical that binds to metal ions. It's used in some medications to prevent unwanted metals from interfering with the drug's stability and effectiveness.
  • UNII PN2ZH5LOQY
    A synthetic red dye approved by the FDA for use in foods, medicines, and cosmetics. It serves as a colorant to make tablets, capsules, and liquids visually distinctive for product identification.
  • UNII 2G86QN327L
    Gelatin is a protein derived from animal collagen, commonly used in medicines as a gelling agent and capsule material. It helps create soft or hard capsule shells that hold and release medication, and can also thicken liquid formulations.
  • UNII 3NXW29V3WO
    Hypromellose is a plant-based thickener made from cellulose. It's used in medicines as a binder to hold ingredients together, a coating for tablets, and a thickener for liquids.
  • UNII EWQ57Q8I5X
    Lactose monohydrate is a natural sugar derived from milk. It serves as a filler and binder in tablets and capsules, helping create the proper size, texture, and consistency of the medicine.
  • UNII 70097M6I30
    Magnesium stearate is a salt made from magnesium and stearic acid, a fatty substance. It's used in tablets and capsules as a lubricant and glidant to help ingredients flow smoothly during manufacturing and prevent sticking.
  • UNII A2I8C7HI9T
    Methylparaben is a preservative derived from benzoic acid that prevents growth of bacteria, fungi, and mold in medicines. It extends the product's shelf life and maintains safety during storage.
  • UNII Z8IX2SC1OH
    Propylparaben is a chemical preservative used to prevent bacterial and fungal growth in medicines and personal care products. It helps extend shelf life and maintain product safety during storage.
  • UNII 368GB5141J
    A detergent and foaming agent derived from coconut or palm oil. In medications, it helps break down and mix oil and water-based ingredients, aids in tablet disintegration, and improves how the drug dissolves and spreads in the mouth or digestive system.
  • UNII DK6Y9P42IN
    Sodium propionate is a salt derived from propionic acid. It's added to medicines as a preservative to prevent bacterial and fungal growth, helping extend shelf life.
  • UNII C151H8M554
    A natural sugar derived from sugar cane or sugar beets. It's used as a sweetener, filler, and binder to improve taste, add bulk, and help hold tablet or capsule ingredients together.
  • UNII 7SEV7J4R1U
    A powder made from a naturally occurring mineral. In medicines, talc works as a glidant and anti-caking agent, helping tablets and capsules flow smoothly during manufacturing and preventing clumping.
  • UNII 15FIX9V2JP
    Titanium dioxide is a bright white mineral powder commonly used as a colorant and opacifying agent. It makes pills and tablets white or lighter in color and helps make coatings non-transparent.

16 inactive ingredients listed in the exact product block matched to this NDC.

Where does this data come from?
Data sourced from official FDA Structured Product Labeling (SPL) via DailyMed — ingredient classCode="IACT" elements from the exact product block matched by this NDC. Label-section narrative from DailyMed / the openFDA label index is shown separately when available.

Inactive ingredient FAQ

Are inactive ingredients the same for every manufacturer?
No. Inactive ingredients can differ by manufacturer, dosage form, strength, and package / product version.
Why might an inactive ingredient be missing?
Some SPLs do not provide a complete structured inactive-ingredient list, and older or unusual labels may only include the information in narrative text.
Can inactive ingredients matter?
Yes. They can matter for allergies, intolerances, dyes, gluten / lactose concerns, preservatives, and formulation differences — but confirm with a pharmacist or the manufacturer when it’s clinically important.

💲 Pricing

A drug doesn't have one price. Each row is a different public payment system, and none is what you'd pay at the counter — that depends on your insurance. The ⓘ on each row explains what it measures.

Price systemPer eachPer package
Retail pharmacies payNADAC · weekly Not in the retail survey — common for institutional, discontinued, or low-volume packs.
Medicaid paysCMS SDUD · 12 mo No recent Medicaid claims on file for this NDC — rare and low-volume NDCs are suppressed in the public data.
Medicare drug plans payPart D · quarterly No Part D plan price is available for this NDC in our data.
ℹ️
No price is published for this exact package yet. CMS surveys NADAC per package size, so a different pack of the same drug often has one.
Try another pack size: 30 capsules 100 capsules 1000 capsules
Where does this data come from?
NADAC (National Average Drug Acquisition Cost) is the CMS weekly pharmacy-acquisition-cost survey — what pharmacies pay. ASP (Average Sales Price) is the CMS Medicare Part B drug-payment file, published quarterly. Medicaid pays is computed by us from CMS State Drug Utilization Data (total reimbursed ÷ units, trailing 12 months) — gross of rebates and inclusive of dispensing fees, so it reflects what Medicaid paid, not an acquisition cost. Medicare drug plans pay is the median negotiated point-of-sale unit cost across plans listing this NDC in the CMS quarterly Prescription Drug Plan pricing files, before rebates. The VA pays is the federal contract price (FSS, and the statutory Big 4 ceiling where listed) from the VA National Acquisition Center pharmaceutical price file. All are free public government data; each measures a different payer, so the figures are not directly comparable.

🔁 Therapeutic equivalents

ProductLabelerPackNADAC/unitTEStatusPrice vs. this
Phenytoin Sodium 100 mg 00904-7416-61 Major 1 capsule $0.147 AB Availability likely —
Phenytoin Sodium 100 mg 50268-0719-13 AvPAK 1 capsule $0.147 AB Availability likely —
Extended Phenytoin Sodium 100 mg 60687-0841-01 American 100 capsules $0.147 AB Availability likely —
Phenytoin Sodium 100 mg 65862-0692-01 Aurobindo 100 capsules $0.147 — Availability likely —
Dilantin 100 mg 58151-0110-01 Viatris 100 capsules $1.739 — Availability likely —
Extended Phenytoin Sodium 100 mg 00615-8556-39 NCS 30 capsules — AB FDA listed —
Phenytoin Sodium 100 mg 29300-0379-01 Unichem 100 capsules — — FDA listed —
Phenytoin Sodium 100 mg 50090-3539-00 A-S 100 capsules — AB FDA listed —
Phenytoin Sodium 100 mg 50090-5700-00 A-S 100 capsules — AB FDA listed —
Phenytoin Sodium 100 mg 51407-0982-01 Golden 100 capsules — AB FDA listed —
Phenytoin Sodium 100 mgthis 51672-4111-00 Sun 10 capsules — AB Discontinued —
Phenytoin Sodium 100 mg 61919-0815-30 DIRECT 30 capsules — AB FDA listed —
Extended Phenytoin Sodium 100 mg 65162-0212-03 Amneal 30 capsules — AB FDA listed —
Phenytoin Sodium 100 mg 67046-0585-03 Coupler 30 capsules — AB FDA listed —
Phenytoin Sodium 100 mg 70518-0107-00 REMEDYREPACK 30 capsules — AB FDA listed —
Extended Phenytoin Sodium 100 mg 70518-2227-00 REMEDYREPACK 30 capsules — AB Discontinued —
Phenytoin Sodium 100 mg 70518-2293-01 REMEDYREPACK 1 capsule — AB FDA listed —
Phenytoin Sodium 100 mg 71610-0869-92 Aphena 270 capsules — AB FDA listed —
Phenytoin Sodium 100 mg 71610-0934-92 Aphena 270 capsules — AB FDA listed —
Phenytoin Sodium 100 mg 72162-1646-00 Bryant 1000 capsules — AB Discontinued —
Extended Phenytoin Sodium 100 mg 72162-2514-00 Bryant 1000 capsules — AB FDA listed —
Phenytoin Sodium 100 mg 82804-0269-72 Proficient 120 capsules — AB FDA listed —
About this product: this is a generic version of the medicine. FDA equivalence ratings are shown when available, and other versions are listed above, least expensive first.
Where does this data come from?
Equivalents are other NDCs of the same ingredient, form and route from the openFDA NDC Directory, ranked least-expensive-first by NADAC. Therapeutic-equivalence (AB) ratings come from the FDA Orange Book; biologics use the FDA Purple Book for biosimilar & interchangeable status.

⏳ Availability & generic status

🏛️
2006
On the market since
Sep 2006
📍
2026
Currently FDA-listed
20 years listed
🔓
·
Generic on the market
this product is a generic
✅This is a generic drug

This product is an FDA-approved generic. Other versions of the same drug are listed under Therapeutic equivalents, least expensive first.

Where does this data come from?
Patents and exclusivity from the FDA Orange Book (small-molecule drugs), refreshed from public FDA data. Generic launch timing is an estimate, not a guarantee.

💊 Medicaid utilization by pack size

Medicaid (SDUD) totals over the four most recent reported quarters for every package size of this drug — handy when a specific package (e.g. a starter/titration pack) carries little or no Medicaid volume on its own.
1000 capsules51672-4111-03 52,199 Rx · $1,393,499
100 capsules51672-4111-01 32,031 Rx · $862,180
10 capsules this page51672-4111-00 No Medicaid data
30 capsules51672-4111-06 No Medicaid data
Drug total (last 4 qtrs): 84,230 Rx · 9,143,842 units · $2,255,679 gross reimbursed
Tap a pack size to open its page. Source: CMS State Drug Utilization Data, last 4 quarters.

📊 Medicare Part D spend CMS · PART D · 2026 (Q1)

Medicare Part D (outpatient prescription) spending for Phenytoin Sodium — the program that covers self-administered drugs. 1 manufacturer.
⚠️ Drug-level data: CMS publishes Part D spending by drug, not by NDC — these figures combine every manufacturer, strength and package size sold under the name Phenytoin Sodium. That’s a different level of aggregation than the Medicaid card above, which is specific to this exact 11-digit NDC (pack size included), so the two aren’t directly comparable.
Period
Total Part D spend
$511.44
Claims incl. refills
18
Beneficiaries
—
Spend / beneficiary
—
Spend / claim
$28.41
Trend by period
💵 About the dollar figures: spending is what Part D plans paid before confidential manufacturer rebates, so the program’s real net cost is lower. A blank patient count means fewer than 11 people — CMS hides counts that small to protect privacy. Source: CMS Medicare Quarterly Part D Spending by Drug (data.cms.gov), updated quarterly.

🔬 Reported adverse events (FAERS)

Read carefully: FAERS reports are voluntary and unverified. Counts are not incidence, do not establish causation, are subject to reporting bias, and cannot be used to compare one drug to another. Shown for signal context only. Reports for Phenytoin Sodium — the ingredient across all brands.

Top reported reactions

Convulsion2,381
Seizure1,751
Fall1,027
Dizziness979
Drug Hypersensitivity946
Headache930
Fatigue883

Age at onset

Neonate12
Infant22
Child26
Adolescent13
Adult550
Elderly305

Reporter sex

20,229 reports
Male · 44%
Female · 55%
Unknown · 1%

Serious outcomes

Hospitalization6,565
Death1,487
Life-threatening812
Disabling618
Reports over time (by year) — tap or hover for the count & year
2019 2021 2023 2026 1,261 0
Most recent year is provisional (FAERS lags ~3 months).
Where does this data come from?
Adverse-event reports from the FDA Adverse Event Reporting System (FAERS) via openFDA. FAERS reports are voluntary and unverified — counts are not incidence and don’t establish causation.

📦 Packaging — all sizes for this product

Package NDCDescription Per unit Per pack Marketing startStatus
51672-4111-00 You're viewing this 10 BLISTER PACK in 1 CARTON (51672-4111-0) / 10 CAPSULE, EXTENDED RELEASE in 1 BLISTER PACK — — 2006-09-05 Discontinued by firm
51672-4111-01 100 CAPSULE, EXTENDED RELEASE in 1 BOTTLE (51672-4111-1) $0.1471 / ea $14.71 2006-09-05 Active
51672-4111-03 1000 CAPSULE, EXTENDED RELEASE in 1 BOTTLE (51672-4111-3) $0.1471 / ea $147.09 2006-09-05 Active
51672-4111-06 30 CAPSULE, EXTENDED RELEASE in 1 BOTTLE (51672-4111-6) — — 2006-09-05 Active

This pack shows little to no recent Medicaid volume — the 1000 capsules pack carries most fills. See all packs ↓

Pack size FAQ

What quantity is in NDC 51672-4111-00?
NDC 51672-4111-00 is listed by the FDA — 10 blister pack in 1 carton / 10 capsule, extended release in 1 blister pack.
What NDC number is used to bill for this package of Phenytoin Sodium 100 mg Capsule, Extended Release?
Bill NDC 51672-4111-00 — the 11-digit billing format is 51672411100. Pharmacy and medical claims use the 11-digit form; the FDA label may print a shorter form of the same code.

Prices are the latest CMS NADAC pharmacy acquisition cost per NDC; per-pack figures are per-unit × pack quantity, shown only when the pack is denominated in the same measure NADAC prices.

🧭 About this NDC listing & data coverage

Finished prescription product No longer marketed (per FDA listing data)
What data is (and isn’t) available for this NDC — tap to expand
NDC identity (package / product / labeler codes) ✓ Available
Labeler ✓ Available
Product & package description ✓ Available
Marketing category & status ✓ Available
Active ingredient / dosage form / route ✓ Available
FDA label (SPL via DailyMed) ✓ Available
Package photos ✓ Available
Inactive ingredients (structured) ✓ Available
NADAC pharmacy acquisition price (CMS) — Not published for this NDC CMS publishes NADAC only for NDCs reported in its retail-pharmacy survey.
Orange Book / therapeutic-equivalence data ✓ Available
HCPCS J-code billing crosswalk — Not published for this NDC Most self-administered / retail products have no J-code — that is normal.
Medicaid utilization (CMS SDUD) — Not published for this NDC CMS reports utilization only for NDCs with Medicaid claims above its privacy threshold.
“Not published” reflects what the public FDA / CMS / NLM sources provide for this exact package code — it is a property of the data feeds, not a judgment about the product.

Questions about this listing

Why is there no price listed?
The pricing shown on our NDC pages comes from CMS NADAC, a voluntary survey of retail community pharmacy invoices. CMS does not publish a NADAC for every NDC — packages outside the retail survey (institutional and hospital products, bulk packages, discontinued items, and many OTC items) may never receive one. A missing price reflects the survey's scope, not this product's actual cost, and does not mean the product is free or unavailable.
What does the discontinued status mean for this NDC?
The labeler reported a marketing end date (or the listing was delisted), so this specific package is no longer actively marketed. Remaining stock may still be dispensed for a time, and the NDC stays valid for historical records and claims — but data feeds (pricing, labeling) typically stop updating for it. Other package sizes or other manufacturers' versions of the same medication may still be marketed — see the equivalents section where available.
Is the NDC printed on the package the same as the 11-digit billing NDC?
Yes, they identify this exact package in different formats. The FDA registers it as 51672-4111-0, which is what is printed on the packaging and shown on DailyMed. Insurance claims use a fixed 11-digit 5-4-2 format, so the short segment is padded with a leading zero: 51672-4111-00, written without dashes as 51672411100. The Identity section at the top of this page lists every form of this code.
What do the three segments of this NDC mean?
In 51672-4111-00, the first segment (51672) is the labeler code FDA assigned to Sun Pharmaceutical Industries, Inc.; the middle segment (4111) identifies this specific product — its ingredient, strength, and dosage form; and the last segment (00) identifies this exact package size and type. Together they name one specific package of one specific product.
Does this product come in other package sizes?
Yes — the FDA directory lists 3 other package presentations of this same product, including 30 capsules (51672-4111-06), 100 capsules (51672-4111-01), 1000 capsules (51672-4111-03). Each has its own NDC and its own page — see the package list near the top of this page.
Who lists this product with the FDA?
Sun Pharmaceutical Industries, Inc. is the labeler of record for this NDC — the company under whose FDA-assigned code the package is listed. The labeler may be the manufacturer itself or a distributor marketing the product under its own code.
Do I need a prescription for this product?
This NDC is listed with FDA as a prescription product, so it is dispensed under a prescriber's order. Your pharmacist can tell you whether any over-the-counter forms of the same medication exist.
This page identifies an FDA-listed package (the NDC) and reports public regulatory and pricing data about the listing. It is reference information, not a medical recommendation — talk to your pharmacist or prescriber about your own medication.
Where does this data come from?
Listing facts (marketing category, packager status, marketing dates) from the FDA openFDA NDC Directory; label availability from DailyMed; pricing coverage from CMS NADAC; equivalence scope from the FDA Orange Book.

📄 Full prescribing information FDA SPL

The complete FDA label for this product — the official prescribing information, verbatim, section by section. Jump with a chip, search within the label, or expand everything.
🎯 Indications and Usage ⏱️ Dosage and Administration 💊 Dosage Forms and Strengths ⛔ Contraindications ⚠️ Warnings and Cautions 🤒 Adverse Reactions 🔄 Drug Interactions 👥 Use in Specific Populations 🤰 Pregnancy 🧒 Pediatric Use 🧓 Geriatric Use 🆘 Overdosage 🧬 Clinical Pharmacology 🧬 Mechanism of Action 📦 How Supplied / Storage and Handling 📦 Storage and Handling 📋 Description 💬 Information for Patients 💬 Medication Guide
🎯 Indications and Usage 65 words ▾

1 INDICATIONS AND USAGE Extended phenytoin sodium capsules are indicated for the treatment of tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures and prevention and treatment of seizures occurring during or following neurosurgery. Extended phenytoin sodium capsules are indicated for the treatment of tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures and prevention and treatment of seizures occurring during or following neurosurgery. ( 1 )

⏱️ Dosage and Administration ~3 min read ▾

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 )

2.1Adult 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.

A major problem in motivating noncompliant patients may also be lessened when the patient can take this drug once a day. However, patients should be cautioned not to miss a dose, inadvertently. Only extended phenytoin sodium capsules are recommended for once-a-day dosing.

Inherent differences in dissolution characteristics and resultant absorption rates of phenytoin due to different manufacturing procedures and/or dosage forms preclude such recommendation for other phenytoin products. When a change in the dosage form or brand is prescribed, careful monitoring of phenytoin serum levels should be carried out. Loading dose: Some authorities have advocated use of an oral loading dose of phenytoin in adults who require rapid steady-state serum levels and where intravenous administration is not desirable.

This dosing regimen should be reserved for patients in a clinic or hospital setting where phenytoin serum levels can be closely monitored. Patients with a history of renal or liver disease should not receive the oral loading regimen. Initially, one gram of extended phenytoin sodium capsules is divided into three doses (400 mg, 300 mg, 300 mg) and administered at two-hour intervals.

Normal maintenance dosage is then instituted 24 hours after the loading dose, with frequent serum level determinations.

2.2Pediatric Dosage The recommended starting dosage for pediatric patients is 5 mg/kg/day by mouth in two or three equally divided doses, with subsequent dosage individualized to a maximum of 300 mg daily in divided doses. A recommended daily maintenance dosage is usually 4 mg/kg/day to 8 mg/kg/day in equally divided doses. Children over 6 years and adolesc…

💊 Dosage Forms and Strengths 63 words ▾

3 DOSAGE FORMS AND STRENGTHS Extended phenytoin sodium capsules, USP are available as: 100 mg: hard, gelatin capsules No. 3 with an opaque orange body and cap containing a white to off-white powder. Capsule is imprinted "TARO PHN 100" in black ink on both body and cap. Extended phenytoin sodium capsules are available as 100 mg extended phenytoin sodium capsules. ( 3 )

⛔ Contraindications 108 words ▾

4 CONTRAINDICATIONS Extended phenytoin sodium capsules are contraindicated in patients with: A history of hypersensitivity to phenytoin, its inactive ingredients, or other hydantoins [see Warnings and Precautions (5.5) ] . Reactions have included angioedema. A history of prior acute hepatotoxicity attributable to phenytoin [see Warnings and Precautions (5.8) ].

Coadministration with delavirdine because of the potential for loss of virologic response and possible resistance to delavirdine or to the class of non-nucleoside reverse transcriptase inhibitors. Hypersensitivity to phenytoin, its ingredients, or other hydantoins ( 4 , 5.5 ) A history of prior acute hepatotoxicity attributable to phenytoin ( 4 , 5.8 ) Coadministration with delavirdine ( 4 )

⚠️ Warnings and Cautions ~3 min read ▾

5 WARNINGS AND PRECAUTIONS Withdrawal Precipitated Seizure: May precipitate status epilepticus. Dose reductions or discontinuation should be done gradually. ( 5.1 ) Suicidal Behavior and Ideation: Monitor patients for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior.

( 5.2 ) Serious Dermatologic Reactions: Discontinue extended phenytoin sodium capsules at the first sign of a rash, unless the rash is clearly not drug-related. If signs or symptoms suggest SJS/TEN, use of this drug should not be resumed and alternative therapy should be considered. ( 5.3 ) Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity: If signs or symptoms of hypersensitivity are present, evaluate the patient immediately.

Discontinue if an alternative etiology cannot be established. ( 5.4 ) Cardiac Effects: Bradycardia and cardiac arrest have been reported. ( 5.6 ) Angioedema: Discontinue immediately if symptoms of angioedema such as facial, perioral, or upper airway swelling occur.

( 5.7 ) Hepatic Injury: Cases of acute hepatotoxicity have been reported with extended phenytoin sodium capsules. If this occurs, immediately discontinue. ( 4 , 5.8 ) Hematopoietic Complications: If occurs, follow-up observation is indicated and an alternative antiepileptic treatment should be used.

( 5.9 )

5.1Withdrawal Precipitated Seizure, Status Epilepticus Abrupt withdrawal of phenytoin in epileptic patients may precipitate status epilepticus. When, in the judgment of the clinician, the need for dosage reduction, discontinuation, or substitution of alternative anticonvulsant medication arises, this should be done gradually. However, in the event of an allergic or hypersensitivity reaction, more rapid substitution of alternative therapy may be necessary.

In this case, alternative therapy should be an anticonvulsant drug not belonging to the hydantoin chemical class.

5.2Suicidal Behavior and Ideation Antiepileptic drugs (AEDs), including extended phenytoin sodium capsules, increase the risk of suicidal thoughts or behavior in patients taking these drugs for any indication. Patients treated with any AED for any indication should be monitored for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior. Pooled analyses of 199 placebo-controlled clinical trials (mono- and adjunctive therapy) of 11 different AEDs showed that patients randomized to one of the AEDs had approximately twice the risk (adjusted Relative Risk 1.8, 95% CI:1.2, 2.7) of suicidal thinking or behavior compared to patients randomized to placebo.

In these trials, which had a median treatment duration of 12 weeks, the estimated incidence rate of suicidal behavior or ideation among 27,863 AED-treated patients was 0.43%, compared to 0.24% among 16,029 placebo-treated patients, representing an increase of approximately one case of suicidal thinking or behavior for every 530 patients treated. There were four suicides in drug-treated patients in the trials and none in placebo-treated patients, but the number is too small to allow any conclusion about drug effect on suicide.

The increased risk of suicidal thoughts or behavior with AEDs was observed as early as one week after starting drug treatment with AEDs and persisted for the duration of treatment assessed. Because most trials included in the analysis did not extend beyond 24 weeks, the risk of suicidal thoughts or behavior beyond 24 weeks could not be assessed. The risk of suicidal thoughts or behavior was generally consistent among drugs in the data analyzed.

The finding of increased risk with AEDs of varying mechanisms of action and across a range of indications suggests that the risk applies to all AEDs used for any indication. The risk did not vary substantially by age (5 years to 100 years) in the clinical trials analyzed. Table 1 shows absolute and relative risk by indication for all e…

🤒 Adverse Reactions ~2 min read ▾

6 ADVERSE REACTIONS The following serious adverse reactions are described elsewhere in the labeling: Withdrawal Precipitated Seizure, Status Epilepticus [see Warnings and Precautions (5.1) ] Suicidal Behavior and Ideation [see Warnings and Precautions (5.2) ] Serious Dermatologic Reactions [see Warnings and Precautions (5.3) ] Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS)/Multiorgan Hypersensitivity [see Warnings and Precautions (5.4) ] Hypersensitivity [see Warnings and Precautions (5.5) ] Cardiac Effects [see Warnings and Precautions (5.6) ] Angioedema [see Warnings and Precautions (5.7) ] Hepatic Injury [see Warnings and Precautions (5.8) ] Hematopoietic Complications [see Warnings and Precautions (5.9) ] Effects on Vitamin D and Bone [see Warnings and Precautions (5.10) ] Exacerbation of Porphyria [see Warnings and Precautions (5.12) ] Teratogenicity and Other Harm to the Newborn [see Warnings and Precautions (5.13) ] Hyperglycemia [see Warnings and Precautions (5.14) ] The following adverse reactions associated with the use of extended phenytoin sodium capsules were identified in clinical studies or postmarketing reports.

Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. Body as a Whole: Allergic reactions in the form of rash and rarely more serious forms and DRESS have been observed, as has angioedema [see Warnings and Precautions (5.3 , 5.4 , 5.7) ] . Anaphylaxis has also been reported.

There have also been reports of coarsening of facial features, systemic lupus erythematosus, periarteritis nodosa, and immunoglobulin abnormalities. Digestive System: Acute hepatic failure, toxic hepatitis, liver damage, nausea, vomiting, constipation, enlargement of the lips, and gingival hyperplasia. Hematologic and Lymphatic System: Hematopoietic complications, some fatal, have occasionally been reported in association with administration of phenytoin.

These have included thrombocytopenia, leukopenia, granulocytopenia, agranulocytosis, and pancytopenia with or without bone marrow suppression. While macrocytosis and megaloblastic anemia have occurred, these conditions usually respond to folic acid therapy. Lymphadenopathy including benign lymph node hyperplasia, pseudolymphoma, lymphoma, and Hodgkin's disease have been reported [see Warnings and Precautions (5.9) ] .

Pure red cell aplasia has also been reported. Laboratory Test Abnormality: Phenytoin may decrease serum concentrations of thyroid hormone (T4 and T3), sometimes with an accompanying increase in thyroid-stimulating hormone (TSH), but usually in the absence of clinical hypothyroidism. Phenytoin may also produce lower than normal values for dexamethasone or metyrapone tests.

Phenytoin may cause increased serum levels of glucose [see Warnings and Precautions (5.14) ] , alkaline phosphatase, and gamma glutamyl transpeptidase (GGT). Nervous System: The most common adverse reactions encountered with phenytoin therapy are nervous system reactions and are usually dose-related. Reactions include nystagmus, ataxia, slurred speech, decreased coordination, somnolence, and mental confusion.

Dizziness, vertigo, insomnia, transient nervousness, motor twitchings, paresthesias, and headaches have also been observed. There have also been rare reports of phenytoin-induced dyskinesias, including chorea, dystonia, tremor and asterixis, similar to those induced by phenothiazine and other neuroleptic drugs. Cerebellar atrophy has been reported, and appears more likely in settings of elevated phenytoin levels and/or long-term phenytoin use [see Warnings and Precautions (5.15) ] .

A predominantly sensory peripheral polyneuropathy has been observed in patients receiving long-term phenytoin therapy. Skin and Appendages: Dermatological manifestations sometimes accompanied by fever have included scarlatiniform or morbilliform rashes. A m…

🔄 Drug Interactions ~2 min read ▾

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 )

7.1Drugs 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. Table 2: Drugs That Affect Phenytoin Concentrations Interacting Agent Examples Drugs that may increase phenytoin serum levels Antiepileptic drugs Ethosuximide, felbamate, oxcarbazepine, methsuximide, topiramate Azoles Fluconazole, ketoconazole, itraconazole, miconazole, voriconazole Antineoplastic agents Capecitabine, fluorouracil Antidepressants Fluoxetine, fluvoxamine, sertraline Gastric acid reducing agents H 2 antagonists (cimetidine), omeprazole Sulfonamides Sulfamethizole, sulfaphenazole, sulfadiazine, sulfamethoxazole-trimethoprim Other Acute alcohol intake, amiodarone, chloramphenicol, chlordiazepoxide, disulfiram, estrogen, fluvastatin, isoniazid, methylphenidate, phenothiazines, salicylates, ticlopidine, tolbutamide, trazodone, warfarin Drugs that may decrease phenytoin serum levels Antacids Antacids may affect absorption of phenytoin.

Calcium carbonate, aluminum hydroxide, magnesium hydroxide Prevention or Management : Phenytoin and antacids should not be taken at the same time of day Antineoplastic agents usually in combination Bleomycin, carboplatin, cisplatin, doxorubicin, methotrexate Antiviral agents Fosamprenavir, nelfinavir, ritonavir Antiepileptic drugs Carbamazepine, vigabatrin Other Chronic alcohol abuse, diazepam, diazoxide, folic acid, reserpine, rifampin, St. John's wort The induction potency of St. John's wort may vary widely based on preparation. , sucralfate, theophylline Drugs that may either increase or decrease phenytoin serum levels Antiepileptic drugs Phenobarbital, valproate sodium Valproate sodium and valproic acid are similar medications.

The term valproate has been used to represent these medications. , valproic acid

7.2Drugs Affected by Phenytoin Table 3 includes commonly occurring drug interactions affected by phenytoin. However, this list is not intended to be inclusive or comprehensive. Individual drug package inserts should be consulted.

The addition or withdrawal of phenytoin during concomitant therapy with these agents may require adjustment of the dose of these agents to achieve optimal clinical outcome. Table 3: Drugs Affected by Phenytoin Interacting Agent Examples Drugs whose efficacy is impaired by phenytoin Azoles Fluconazole, ketoconazole, itraconazole, posaconazole, voriconazole Antineoplastic agents Irinotecan, paclitaxel, teniposide Delavirdine Phenytoin can substantially reduce the concentrations of delavirdine. This can lead to loss of virologic response and possible resistance [see Contraindications (4) ].

Neuromuscular blocking agents Cisatracurium, pancuronium, rocuronium and vecuronium: resistance to the neuromuscular blocking action of the nondepolarizing neuromuscular blocking agents has occurred in patients chronically administered phenytoin. Whether or not phen…

👥 Use in Specific Populations ~2 min read ▾

8 USE IN SPECIFIC POPULATIONS Pregnancy: Prenatal exposure to phenytoin may increase the risks for congenital malformations and other adverse developmental outcomes. ( 5.13 , 8.1 ) Renal and/or Hepatic Impairment or Hypoalbuminemia: Monitor unbound phenytoin concentrations in these patients. ( 8.6 )

8.1Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to antiepileptic drugs (AEDs), such as extended phenytoin sodium capsules, during pregnancy. Physicians are advised to recommend that pregnant patients taking extended phenytoin sodium capsules enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry. This can be done by calling the toll free number 1-888-233-2334, and must be done by patients themselves.

Information on the registry can also be found at the website http://www.aedpregnancyregistry.org/ Risk Summary In humans, prenatal exposure to phenytoin may increase the risks for congenital malformations and other adverse developmental outcomes. Prenatal phenytoin exposure is associated with an increased incidence of major malformations, including orofacial clefts and cardiac defects. In addition, the fetal hydantoin syndrome, a pattern of abnormalities including dysmorphic skull and facial features, nail and digit hypoplasia, growth abnormalities (including microcephaly), and cognitive deficits has been reported among children born to epileptic women who took phenytoin alone or in combination with other antiepileptic drugs during pregnancy [see Data ] .

There have been several reported cases of malignancies, including neuroblastoma, in children whose mothers received phenytoin during pregnancy. Administration of phenytoin to pregnant animals resulted in an increased incidence of fetal malformations and other manifestations of developmental toxicity (including embryofetal death, growth impairment, and behavioral abnormalities) in multiple species at clinically relevant doses [see Data ]. In the U.S. general population, the estimated background risk of major birth defects and of miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.

The background risk of major birth defects and miscarriage for the indicated population is unknown. Clinical Considerations Disease-associated maternal risk An increase in seizure frequency may occur during pregnancy because of altered phenytoin pharmacokinetics. Periodic measurement of serum phenytoin concentrations may be valuable in the management of pregnant women as a guide to appropriate adjustment of dosage [see Dosage and Administration (2.3 , 2.7) ] .

However, postpartum restoration of the original dosage will probably be indicated [see Clinical Pharmacology (12.3) ]. Fetal/Neonatal Adverse Reactions A potentially life-threatening bleeding disorder related to decreased levels of vitamin K-dependent clotting factors may occur in newborns exposed to phenytoin in utero . This drug-induced condition can be prevented with vitamin K administration to the mother before delivery and to the neonate after birth.

Data Human Data Meta-analyses using data from published observational studies and registries have estimated an approximately 2.4-fold increased risk for any major malformation in children with prenatal phenytoin exposure compared to controls. An increased risk of heart defects, facial clefts, and digital hypoplasia has been reported. The fetal hydantoin syndrome is a pattern of congenital anomalies including craniofacial anomalies, nail and digital hypoplasia, prenatal-onset growth deficiency, and neurodevelopmental deficiencies.

Animal Data Administration of phenytoin to pregnant rats, rabbits, and mice during organogenesis resulted in embryofetal death, fetal malformations, and decreased fetal growth. Malformations (including craniofacial, cardiovascular, neural, limb, and digit abnormalities) were observed in rats, rabbits, and mice at doses as low as 100 mg/kg…

🤰 Pregnancy ~2 min read ▾

8.1Pregnancy Pregnancy Exposure Registry There is a pregnancy exposure registry that monitors pregnancy outcomes in women exposed to antiepileptic drugs (AEDs), such as extended phenytoin sodium capsules, during pregnancy. Physicians are advised to recommend that pregnant patients taking extended phenytoin sodium capsules enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry. This can be done by calling the toll free number 1-888-233-2334, and must be done by patients themselves.

Information on the registry can also be found at the website http://www.aedpregnancyregistry.org/ Risk Summary In humans, prenatal exposure to phenytoin may increase the risks for congenital malformations and other adverse developmental outcomes. Prenatal phenytoin exposure is associated with an increased incidence of major malformations, including orofacial clefts and cardiac defects. In addition, the fetal hydantoin syndrome, a pattern of abnormalities including dysmorphic skull and facial features, nail and digit hypoplasia, growth abnormalities (including microcephaly), and cognitive deficits has been reported among children born to epileptic women who took phenytoin alone or in combination with other antiepileptic drugs during pregnancy [see Data ] .

There have been several reported cases of malignancies, including neuroblastoma, in children whose mothers received phenytoin during pregnancy. Administration of phenytoin to pregnant animals resulted in an increased incidence of fetal malformations and other manifestations of developmental toxicity (including embryofetal death, growth impairment, and behavioral abnormalities) in multiple species at clinically relevant doses [see Data ]. In the U.S. general population, the estimated background risk of major birth defects and of miscarriage in clinically recognized pregnancies is 2% to 4% and 15% to 20%, respectively.

The background risk of major birth defects and miscarriage for the indicated population is unknown. Clinical Considerations Disease-associated maternal risk An increase in seizure frequency may occur during pregnancy because of altered phenytoin pharmacokinetics. Periodic measurement of serum phenytoin concentrations may be valuable in the management of pregnant women as a guide to appropriate adjustment of dosage [see Dosage and Administration (2.3 , 2.7) ] .

However, postpartum restoration of the original dosage will probably be indicated [see Clinical Pharmacology (12.3) ]. Fetal/Neonatal Adverse Reactions A potentially life-threatening bleeding disorder related to decreased levels of vitamin K-dependent clotting factors may occur in newborns exposed to phenytoin in utero . This drug-induced condition can be prevented with vitamin K administration to the mother before delivery and to the neonate after birth.

Data Human Data Meta-analyses using data from published observational studies and registries have estimated an approximately 2.4-fold increased risk for any major malformation in children with prenatal phenytoin exposure compared to controls. An increased risk of heart defects, facial clefts, and digital hypoplasia has been reported. The fetal hydantoin syndrome is a pattern of congenital anomalies including craniofacial anomalies, nail and digital hypoplasia, prenatal-onset growth deficiency, and neurodevelopmental deficiencies.

Animal Data Administration of phenytoin to pregnant rats, rabbits, and mice during organogenesis resulted in embryofetal death, fetal malformations, and decreased fetal growth. Malformations (including craniofacial, cardiovascular, neural, limb, and digit abnormalities) were observed in rats, rabbits, and mice at doses as low as 100 mg/kg, 75 mg/kg, and 12.5 mg/kg, respectively.

🧒 Pediatric Use 57 words ▾

8.4Pediatric Use Initially, 5 mg/kg/day in two or three equally divided doses, with subsequent dosage individualized to a maximum of 300 mg daily. A recommended daily maintenance dosage is usually 4 mg/kg to 8 mg/kg. Children over 6 years and adolescents may require the minimum adult dosage (300 mg/day) [see Dosage and Administration (2.2) ] .

🧓 Geriatric Use 32 words ▾

8.5Geriatric Use Phenytoin clearance tends to decrease with increasing age [see Clinical Pharmacology (12.3) ] . Lower or less frequent dosing may be required [see Dosage and Administration (2.6) ] .

🆘 Overdosage ~1 min read ▾

10 OVERDOSAGE The lethal dose in pediatric patients is not known. The lethal dose in adults is estimated to be 2 grams to 5 grams. The initial symptoms are nystagmus, ataxia, and dysarthria.

Other signs are tremor, hyperreflexia, lethargy, slurred speech, blurred vision, nausea, and vomiting. The patient may become comatose and hypotensive. Bradycardia and cardiac arrest have been reported [see Warnings and Precautions (5.6) ] .

Death is caused by respiratory and circulatory depression. There are marked variations among individuals with respect to phenytoin serum levels where toxicity may occur. Nystagmus, on lateral gaze, usually appears at 20 mcg/mL, ataxia at 30 mcg/mL; dysarthria and lethargy appear when the serum concentration is over 40 mcg/mL, but as high a concentration as 50 mcg/mL has been reported without evidence of toxicity.

As much as 25 times the therapeutic dose has been taken to result in a serum concentration over 100 mcg/mL with complete recovery. Irreversible cerebellar dysfunction and atrophy have been reported. Treatment: Treatment is nonspecific since there is no known antidote.

The adequacy of the respiratory and circulatory systems should be carefully observed and appropriate supportive measures employed. Hemodialysis can be considered since phenytoin is not completely bound to plasma proteins. Total exchange transfusion has been used in the treatment of severe intoxication in pediatric patients.

In acute overdosage the possibility of other CNS depressants, including alcohol, should be borne in mind.

🧬 Clinical Pharmacology ~3 min read ▾

12 CLINICAL PHARMACOLOGY

12.1Mechanism of Action The precise mechanism by which phenytoin exerts its therapeutic effect has not been established but is thought to involve the voltage-dependent blockade of membrane sodium channels resulting in a reduction in sustained high-frequency neuronal discharges.

12.3Pharmacokinetics Absorption For extended phenytoin sodium capsules, peak serum levels occur 4 to 12 hours after administration. Steady-state therapeutic levels are achieved at least 7 to 10 days (5 to 7 half-lives) after initiation of therapy with recommended doses of 300 mg/day. When serum level determinations are necessary, they should be obtained at least 5 to 7 half-lives after treatment initiation, dosage change, or addition or subtraction of another drug to the regimen so that equilibrium or steady-state will have been achieved.

Distribution Phenytoin is extensively bound to serum plasma proteins. Elimination The plasma half-life in man after oral administration of phenytoin averages 22 hours, with a range of 7 to 42 hours. Metabolism Phenytoin is primarily metabolized by the hepatic cytochrome P450 enzyme CYP2C9 and to a lesser extent by CYP2C19.

Because phenytoin is hydroxylated in the liver by an enzyme system which is saturable at high serum levels, small incremental doses may increase the half-life and produce very substantial increases in serum levels, when these are in the upper range. The steady-state level may be disproportionately increased, with resultant intoxication, from an increase in dosage of 10% or more. In most patients maintained at a steady dosage, stable phenytoin serum levels are achieved.

There may be wide interpatient variability in phenytoin serum levels with equivalent dosages. Patients with unusually low levels may be noncompliant or hypermetabolizers of phenytoin. Unusually high levels result from liver disease, variant CYP2C9 and CYP2C19 alleles, or drug interactions which result in metabolic interference.

The patient with large variations in phenytoin serum levels, despite standard doses, presents a difficult clinical problem. Serum level determinations in such patients may be particularly helpful. As phenytoin is highly protein bound, free phenytoin levels may be altered in patients whose protein binding characteristics differ from normal.

Excretion Most of the drug is excreted in the bile as inactive metabolites which are then reabsorbed from the intestinal tract and excreted in the urine. Urinary excretion of phenytoin and its metabolites occurs partly with glomerular filtration but, more importantly, by tubular secretion. Specific Populations Age: Geriatric Population: Phenytoin clearance tends to decrease with increasing age (20% less in patients over 70 years of age relative to that in patients 20 to 30 years of age).

Since phenytoin clearance is decreased slightly in elderly patients, lower or less frequent dosing may be required [see Dosage and Administration (2.6) ]. Sex/Race: Gender and race have no significant impact on phenytoin pharmacokinetics. Renal or Hepatic Impairment: Increased fraction of unbound phenytoin in patients with renal or hepatic disease, or in those with hypoalbuminemia has been reported.

Pregnancy: It has been reported in the literature that the plasma clearance of phenytoin generally increased during pregnancy, reached a peak in the third trimester and returned to the level of pre-pregnancy after few weeks or months of delivery. Drug Interaction Studies Phenytoin is primarily metabolized by the hepatic cytochrome P450 enzyme CYP2C9 and to a lesser extent by CYP2C19. Phenytoin is a potent inducer of hepatic drug-metabolizing enzymes [see Drug Interactions (7.1 , 7.2) ] .

12.5Pharmacogenomics CYP2C9 activity is decreased in individuals with genetic variants such as the CYP2C9*2 and CYP2C9*3 alleles. Carriers of variant alleles, resulting in intermediate (e.g., *1/*3, *2/*2) or poor metabolism (e.g., *2/*3, *3/*3) have decreased clearance of phenytoin. Oth…

🧬 Mechanism of Action 39 words ▾

12.1Mechanism of Action The precise mechanism by which phenytoin exerts its therapeutic effect has not been established but is thought to involve the voltage-dependent blockade of membrane sodium channels resulting in a reduction in sustained high-frequency neuronal discharges.

📦 How Supplied / Storage and Handling 85 words ▾

16 HOW SUPPLIED/STORAGE AND HANDLING

16.1How Supplied Extended Phenytoin Sodium Capsules USP, 100 mg are hard gelatin capsules No. 3 with an opaque orange body and cap, imprinted "TARO PHN 100" in black ink. They are available in: Bottles of 30 NDC 51672-4111-6 Bottles of 100 NDC 51672-4111-1 Bottles of 1000 NDC 51672-4111-3 Unit Dose of 100's NDC 51672-4111-0

16.2Storage and Handling Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature]. Preserve in tight, light-resistant containers. Protect from moisture.

📦 Storage and Handling 25 words ▾

16.2Storage and Handling Store at 20° to 25°C (68° to 77°F) [see USP Controlled Room Temperature]. Preserve in tight, light-resistant containers. Protect from moisture.

📋 Description 137 words ▾

11 DESCRIPTION Phenytoin is related to the barbiturates in chemical structure, but has a five-membered ring. The chemical name is 5,5-diphenyl-2,4 imidazolidinedione, having the following structural formula: Each extended phenytoin sodium capsule, USP for oral administration contains 100 mg phenytoin sodium, USP. Also contains confectioner's sugar, hypromellose, lactose monohydrate, magnesium stearate, and talc.

The capsule shell contains benzyl alcohol, black ink, butylparaben, D&C Yellow #10, edetate calcium disodium, FD&C Red #3, gelatin, methylparaben, propylparaben, sodium lauryl sulfate, sodium propionate, and titanium dioxide. Product in vivo performance is characterized by a slow and extended rate of absorption with peak blood concentrations expected in 4 to 12 hours as contrasted to Prompt Phenytoin Sodium Capsules, USP with a rapid rate of absorption with peak blood concentration expected in 1½ to 3 hours. Meets USP Dissolution Test 2.

Chemical Structure

💬 Information for Patients ~3 min read ▾

17 PATIENT COUNSELING INFORMATION Advise patients to read the FDA-approved patient labeling (Medication Guide). Administration Information Advise patients taking phenytoin of the importance of adhering strictly to the prescribed dosage regimen, and of informing the physician of any clinical condition in which it is not possible to take the drug orally as prescribed, e.g., surgery, etc. Advise patients not to use capsules which are discolored.

Withdrawal of Antiepileptic Drugs Advise patients not to discontinue use of extended phenytoin sodium capsules without consulting with their healthcare provider. Extended phenytoin sodium capsules should normally be gradually withdrawn to reduce the potential for increased seizure frequency and status epilepticus [see Warnings and Precautions (5.1) ] . Suicidal Ideation and Behavior Counsel patients, their caregivers, and families that AEDs, including extended phenytoin sodium capsules, may increase the risk of suicidal thoughts and behavior and advise them of the need to be alert for the emergence or worsening of symptoms of depression, any unusual changes in mood or behavior, or the emergence of suicidal thoughts, behavior, or thoughts about self-harm.

Behaviors of concern should be reported immediately to healthcare providers [see Warnings and Precautions (5.2) ] . Serious Dermatologic Reactions Advise patients of the early signs and symptoms of severe cutaneous adverse reactions and to report any occurrence immediately to a physician [see Warnings and Precautions (5.3) ] . Potential Signs of Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS) and Other Systemic Reactions Advise patients of the early toxic signs and symptoms of potential hematologic, dermatologic, hypersensitivity, or hepatic reactions.

These symptoms may include, but are not limited to, fever, sore throat, rash, ulcers in the mouth, easy bruising, lymphadenopathy, facial swelling, and petechial or purpuric hemorrhage, and in the case of liver reactions, anorexia, nausea/vomiting, or jaundice. Advise the patient that, because these signs and symptoms may signal a serious reaction, that they must report any occurrence immediately to a physician. In addition, advise the patient that these signs and symptoms should be reported even if mild or when occurring after extended use [see Warnings and Precautions (5.3 , 5.4 , 5.5 , 5.8 , 5.9) ] .

Cardiac Effects Counsel patients that cases of bradycardia and cardiac arrest have been reported, both at recommended phenytoin doses and levels, and in association with phenytoin toxicity. Patients should report cardiac signs or symptoms to their healthcare provider [see Warnings and Precautions (5.6) and Overdosage (10) ]. Angioedema Advise patients to discontinue extended phenytoin sodium capsules and seek immediate medical care if they develop signs or symptoms of angioedema, such as facial, perioral, or upper airway swelling [see Warnings and Precautions (5.7) ] .

Effects of Alcohol Use and Other Drugs and Over-the-Counter Drug Interactions Caution patients against the use of other drugs or alcoholic beverages without first seeking their physician's advice [Drug Interactions (7.1, 7.2)] . Inform patients that certain over-the-counter medications (e.g., antacids, cimetidine, and omeprazole), vitamins (e.g., folic acid), and herbal supplements (e.g., St. John's wort) can alter their phenytoin levels.

Hyperglycemia Advise patients that extended phenytoin sodium capsules may cause an increase in blood glucose levels [see Warnings and Precautions (5.14) ] . Gingival Hyperplasia Advise patients of the importance of good dental hygiene in order to minimize the development of gingival hyperplasia and its complications. Neurologic Effects Counsel patients that extended phenytoin sodium capsules may cause dizziness, gait disturbance, decreased coordination and somnolence.

Advise patients taking extended phenytoin sodium capsules not to drive, operate complex machinery, or engage in…

💬 Medication Guide ~3 min read ▾

This Medication Guide has been approved by the U.S. Food and Drug Administration. Revised: September 2024 5200710 0924 Dispense with Medication Guide available at: https://www.taro.com/usa-medication-guides MEDICATION GUIDE Extended Phenytoin (fen´ i toyn) Sodium Capsules What is the most important information I should know about extended phenytoin sodium capsules?

Do not stop taking extended phenytoin sodium capsules without first talking to your healthcare provider. Stopping extended phenytoin sodium capsules suddenly can cause serious problems. Stopping a seizure medicine suddenly can cause you to have seizures more often or seizures that will not stop (status epilepticus).

Like other antiepileptic drugs, extended phenytoin sodium capsules may cause suicidal thoughts or actions in a very small number of people, about 1 in 500. Call a healthcare provider right away if you have any of these symptoms, especially if they are new, worse, or worry you: Thoughts about suicide or dying Attempts to commit suicide New or worse depression New or worse anxiety Feeling agitated or restless Panic attacks Trouble sleeping (insomnia) New or worse irritability Acting aggressive, being angry, or violent Acting on dangerous impulses An extreme increase in activity and talking (mania) Other unusual changes in behavior or mood Suicidal thoughts or actions can be caused by things other than medicines.

If you have suicidal thoughts or actions, your healthcare provider may check for other causes. How can I watch for early symptoms of suicidal thoughts and actions? Pay attention to any changes, especially sudden changes, in mood, behaviors, thoughts, or feelings.

Keep all follow-up visits with your healthcare provider as scheduled. Call your healthcare provider between visits as needed, especially if you are worried about symptoms. Extended phenytoin sodium capsules can cause a type of serious allergic reaction that may affect different parts of the body such as your liver, kidneys, blood, heart, skin or other parts of your body.

These can be very serious and cause death. Call your healthcare provider right away if you have any or all of these symptoms: Fever Rash Swollen lymph glands Swelling of your face, eye, lips, or tongue Trouble swallowing or breathing Sore throat Sores in your mouth Bruise easily Purple or red spots on your skin Increase infections Not wanting to eat (anorexia) Nausea Vomiting Yellowing of the skin and the white part of your eyes (jaundice) Call your healthcare provider even if the symptoms are mild or if you have been taking extended phenytoin sodium capsules for an extended period of time.

These symptoms can be a sign of a serious allergic reaction. Phenytoin can cause problems with your heart, including a slow heartbeat. Let your healthcare provider know right away if you have any of these symptoms: dizziness tiredness feeling like your heart is beating slowly or skipping beats chest pain What are extended phenytoin sodium capsules?

Extended phenytoin sodium capsules are a prescription medicine used to treat certain types of seizures called tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures. Do not take extended phenytoin sodium capsules if you: Are allergic to phenytoin or any of the ingredients in extended phenytoin sodium capsules. See the end of this leaflet for a complete list of ingredients in extended phenytoin sodium capsules.

Have had an allergic reaction to CEREBYX ® (fosphenytoin), PEGANONE (ethotoin), or MESANTOIN (mephenytoin). Have had liver problems from taking phenytoin. Take delavirdine.

Before taking extended phenytoin sodium capsules, tell your healthcare provider about all of your medical conditions, including if you: Have or have had depression, mood problems, or suicidal thoughts or behavior Have had an allergic reaction to a medicine similar to extended phenytoin sodium capsules called carboxamides, barbiturates, succinimides, and oxazolidinediones Have or had liver or kidney problem…

Source: FDA Structured Product Labeling, mirrored from DailyMed / openFDA. Prefer the government’s original formatting? View this label on DailyMed ↗
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For educational and professional reference only — not medical advice. Pricing reflects published NADAC and CMS ASP (free public data) and may differ from your acquisition cost; always verify before billing or dispensing.