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Phenytoin Sodium Extended Capsule — prescription drug image

Phenytoin Sodium Extended

Phenytoin Sodium Extended 100MG

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What is Phenytoin Sodium Extended?

Phenytoin Sodium Extended is a medication used to help control seizures. It works by stabilizing electrical activity in the brain, helping to prevent seizures from occurring.

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What is Phenytoin Sodium Extended ?

Phenytoin Sodium Extended is a medication used to help control seizures. It works by stabilizing electrical activity in the brain, helping to prevent seizures from occurring.

Source: MedlinePlus, U.S. National Library of Medicine

  • Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing
  • Blistering, peeling, or red skin rash
  • Bone fractures, pain, tenderness, or aching, pain in the back, ribs, arms, or legs, decrease in height
  • Dark urine or pale stools, nausea, vomiting, loss of appetite, stomach pain, yellow skin or eyes
  • Severe confusion, problems with balance or walking, slurred speech, tremors
  • Unusual bleeding, bruising, or weakness
  • Feeling agitated, depressed, nervous, or irritable, thoughts of hurting yourself or others, unusual mood or behavior
  • Slow growth in children
  • Slow heartbeat, chest pain or discomfort, lightheadedness, dizziness or fainting
  • Fever, chills, cough, sore throat, body aches
  • Keep all medicine out of the reach of children. Never share your medicine with anyone.
  • This medicine may make you bleed, bruise, or get infections more easily. Take precautions to prevent illness and injury. Wash your hands often.
  • It is not safe to take this medicine during pregnancy. It could harm an unborn baby. Tell your doctor right away if you become pregnant.
  • Tell your doctor if you are breastfeeding, or if you have kidney disease, liver disease, heart disease, diabetes, porphyria, or a history of depression or mental problems.
  • This medicine may cause the following problems:Changes in mood or behavior, including thoughts of suicideSerious skin reactions, including Stevens-Johnson syndrome, toxic epidermal necrolysis, and acute generalized exanthematous pustulosis (AGEP)Drug reaction with eosinophilia and systemic symptoms (DRESS), which may damage organs, including the liver, kidney, or heartHeart problems (including slow heartbeat)Liver problemsDecreased bone densityHigh blood sugar levels
  • This medicine may make you drowsy. Do not drive or do anything else that could be dangerous until you know how this medicine affects you.
  • This medicine may damage your gums. Brush and floss your teeth regularly and visit your dentist to help prevent these problems.
  • Do not stop using this medicine suddenly. Your doctor will need to slowly decrease your dose before you stop it completely.
  • Tell any doctor or dentist who treats you that you are using this medicine. This medicine may affect certain medical test results.
  • Your doctor will do lab tests at regular visits to check on the effects of this medicine. Keep all appointments.
What is phenytoin sodium extended used for?
Phenytoin sodium extended is FDA-approved to control tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures, and to prevent and treat seizures during or after neurosurgery. It reduces abnormal electrical activity in the brain.
Is phenytoin sodium extended the same as Dilantin?
Yes. Phenytoin sodium extended is the generic version of the brand-name medicines Dilantin and Phenytek. It contains the same active ingredient and works the same way, usually at a lower cash price.
What are the most serious side effects of phenytoin?
The most serious risks include severe skin reactions (Stevens-Johnson syndrome, toxic epidermal necrolysis, and DRESS), which are more likely in people of Asian ancestry carrying the HLA-B*1502 gene; suicidal thoughts or behavior; and birth defects if taken during pregnancy. The injectable form has a boxed warning for heart problems with rapid IV infusion. Seek medical help right away if you develop a rash, fever, or swelling.
Why do you need blood tests while taking phenytoin?
Phenytoin has a narrow therapeutic index, so the safe and effective range is small. Blood tests let your doctor confirm the level in your body is high enough to control seizures but not so high that it becomes toxic, and adjust your dose as needed.
Can you stop taking phenytoin suddenly?
No. Stopping phenytoin abruptly can trigger seizures, including prolonged, dangerous ones. If you and your doctor decide to stop or switch medicines, it should be done gradually under medical supervision.
How much does Phenytoin Sodium Extended cost without insurance?
The price of Phenytoin Sodium Extended without insurance varies by pharmacy, dosage, and quantity. Rx.com compares cash prices at more than 60,000 US pharmacies so you can find the lowest price near you.
What are the common side effects of Phenytoin Sodium Extended?
Common side effects of Phenytoin Sodium Extended may include: Allergic reaction: Itching or hives, swelling in your face or hands, swelling or tingling in your mouth or throat, chest tightness, trouble breathing, Blistering, peeling, or red skin rash, Bone fractures, pain, tenderness, or aching, pain in the back, ribs, arms, or legs, decrease in height, Dark urine or pale stools, nausea, vomiting, loss of appetite, stomach pain, yellow skin or eyes, Severe confusion, problems with balance or walking, slurred speech, tremors. This is not a complete list — consult your pharmacist or doctor for full side effect information.
Is there a generic version of Phenytoin Sodium Extended?
Generic versions may be available for Phenytoin Sodium Extended. Generics contain the same active ingredients as brand-name drugs and are typically 80–90% cheaper. Search Phenytoin Sodium Extended on Rx.com to compare generic and brand prices at pharmacies near you.
What is the cheapest pharmacy for Phenytoin Sodium Extended?
The cheapest pharmacy for Phenytoin Sodium Extended depends on your location and dosage. Rx.com compares prices at CVS, Walgreens, Walmart, Kroger, Costco, and thousands of independent pharmacies. Enter your ZIP code on Rx.com to find the lowest price for Phenytoin Sodium Extended near you.

Phenytoin Sodium Extended Coupons & Prices

Phenytoin Sodium Extended 100MG

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Phenytoin Sodium Extended Capsule — prescription drug image
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Phenytoin Sodium Extended 100mg (90)
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Looking for a phenytoin sodium extended coupon? Phenytoin sodium (extended-release) is the low-cost generic version of Dilantin and Phenytek, a long-used anticonvulsant that helps control seizures. Because it is a widely stocked generic, the cash price is already modest, but what you pay can vary a lot from one pharmacy to the next. Enter your ZIP above to see today's price and compare across more than 60,000 pharmacies with a free Rx.com discount, so you can find the lowest price near you.

What is phenytoin sodium extended and how does it work?

Phenytoin sodium (extended-release) is an anticonvulsant, or antiepileptic, in the hydantoin class. It is FDA-approved to control tonic-clonic (grand mal) and psychomotor (temporal lobe) seizures, and to prevent and treat seizures that occur during or after neurosurgery. It works by decreasing abnormal electrical activity in the brain. The extended-release form is designed to be taken on a regular schedule to keep a steady level of medicine in your body.

Phenytoin is sold under the brand names Dilantin and Phenytek, and the generic is available. The extended-release capsules are the same medicine as brand-name Dilantin at a much lower cash price.

How much does phenytoin sodium extended cost without insurance?

As a generic, phenytoin sodium extended is one of the more affordable seizure medicines, but prices are not the same everywhere. Two pharmacies on the same street can list very different cash prices, which is exactly why comparing matters. Rx.com checks prices across more than 60,000 U.S. pharmacies so you can see who is lowest in your area. Enter your ZIP above to see today's price and print or show a free discount at the pharmacy counter.

The brand-name maker of Dilantin also offers a manufacturer savings program on its official Dilantin website; eligibility and terms vary and typically exclude government insurance, so read the details there. For the generic, a cash discount is usually the simplest way to keep costs down.

Phenytoin alternatives and related seizure medicines

Phenytoin is one of several medicines used to manage seizures. Your prescriber chooses based on your seizure type, other health conditions, pregnancy plans, and how you tolerate side effects. Never switch medicines on your own. Related options you may see include:

You can compare cash prices on each of these with Rx.com to see which is most affordable at your pharmacy.

Important safety information

Phenytoin has a narrow therapeutic index, meaning the difference between a helpful dose and a toxic one is small, so your doctor will order blood tests to keep your level in range. It can cause serious skin reactions, including Stevens-Johnson syndrome, toxic epidermal necrolysis, and DRESS; the risk is higher in people of Asian ancestry who carry the HLA-B*1502 gene, and genetic testing may be considered. Like other antiseizure medicines, it carries a class-wide risk of suicidal thoughts or behavior. It can cause fetal harm and birth defects (fetal hydantoin syndrome) during pregnancy.

Common effects include gum overgrowth, involuntary eye movement (nystagmus), unsteady walking (ataxia), and drowsiness, and phenytoin interacts with many other drugs because it is a strong liver enzyme inducer. Do not stop taking it suddenly, as this can trigger seizures. The injectable form carries a boxed warning about heart problems with rapid IV infusion. This information is not medical advice; talk with your doctor or pharmacist about your specific situation and report any concerning symptoms right away.

Sources & accuracy

This Phenytoin Sodium Extended information was written and reviewed against authoritative U.S. medical sources — MedlinePlus (U.S. National Library of Medicine), DailyMed, and FDA prescribing information — and checked for accuracy. It is provided for education and is not a substitute for professional medical advice.

Verify the official label: Phenytoin Sodium Extended on DailyMed (FDA)

Reviewed against FDA labeling · Last reviewed July 2026

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Medical disclaimer: This information is provided for general educational purposes only and is not medical advice. It is not a substitute for professional diagnosis or treatment. Always consult a licensed physician, pharmacist, or other qualified healthcare provider before starting, stopping, or changing any medication or treatment. Never disregard professional medical advice or delay seeking it because of something you read here. If you think you may have a medical emergency, call your doctor or 911 immediately.


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