1 What is Dilantin?

Brand: Dilantin, Dilantin-125, Dilantin Infatabs, Phenytek, Dilantin-30

Generic: Phenytoin

Dilantin is an anti-convulsant. It is used to control seizures when treating epilepsy. It is also used to prevent and treat seizures that may occur during brain surgery.

This medication is only available with your doctor’s prescription. This medication is available in the following forms:

  • Suspension
  • Chewable Tablet
  • Extended-Release Capsule
  • Capsule

2 What to Know Before Using

Before using Dilantin, you must know all about the risks and complications associated with it. This is a decision that you and your doctor will make together.

For this medication, there are many things that need to be considered:

Allergies: Inform your doctor if you have ever had an allergic reaction to any other medications. It is also important to inform your doctor of any non-medicine allergies such as foods, dyes, preservatives or animals.

Pediatric: Up-to-date Pediatric Appropriate studies have not indicated any problems that would limit the use of this medication.

Geriatric: No appropriate studies have been performed on the relationship of age to the effects of this medication in elderly patients. Safety and efficacy have not been established.

Pregnancy: This medication is listed as Pregnancy Category D. This means that studies in pregnant women have demonstrated a risk to the unborn child. However, the benefits of this medication in a life-threatening situation or serious disease may outweigh the potential risk.

Breastfeeding: There are no up-to-date studies in women for determining infant risk when using this medication while breastfeeding. Weigh the potential risks with the benefits before taking this medication while breastfeeding.

Drug Interactions: Certain medications should not be used together. However, in certain cases, two medications may be used together, even if an interaction might occur. In these cases, your doctor may want to change your dose or take other precautions.

When taking this medication, it is important that you inform your doctor if you are taking any of the medications listed below. The following interactions were selected on the basis of potential significance and are not all-inclusive. Using this medication with any of the following is not recommended.

Your doctor may decide not to treat you with this medication, or change some of the other medications you take:

  • Amifampridine
  • Artemether
  • Atazanavir
  • Boceprevir
  • Cobicistat
  • Daclatasvir
  • Dasabuvir
  • Delamanid
  • Delavirdine
  • Elvitegravir
  • Isavuconazonium Sulfate
  • Lurasidone
  • Maraviroc
  • Ombitasvir
  • Paritaprevir
  • Piperaquine
  • Praziquantel
  • Ranolazine
  • Rilpivirine
  • Ritonavir
  • Telaprevir

Using this medication with any of the following medication is not recommended, but may be unavoidable in some cases.

Your doctor may make the decision not to treat you with this medication or change some of the other medications you take:

  • Abiraterone
  • Afatinib
  • Aluminum Carbonate, Basic
  • Aluminum Hydroxide
  • Aluminum Phosphate
  • Apazone
  • Apixaban
  • Apremilast
  • Aprepitant
  • Aripiprazole
  • Axitinib
  • Beclamide
  • Bedaquiline
  • Blinatumomab
  • Bortezomib
  • Bosutinib
  • Brexpiprazole
  • Bupropion
  • Cabozantinib
  • Calcium Carbonate
  • Canagliflozin
  • Carbamazepine
  • Cariprazine
  • Ceritinib
  • Clarithromycin
  • Clozapine
  • Cobimetinib
  • Crizotinib
  • Cyclophosphamide
  • Dabrafenib
  • Dasatinib
  • Deferasirox
  • Diazepam
  • Diazoxide
  • Dihydroxyaluminum Aminoacetate
  • Dihydroxyaluminum Sodium Carbonate
  • Dolutegravir
  • Donepezil
  • Doxorubicin
  • Doxorubicin Hydrochloride Liposome
  • Dronedarone
  • Edoxaban
  • Eliglustat
  • Enzalutamide
  • Erlotinib
  • Eslicarbazepine Acetate
  • Ethosuximide
  • Etravirine
  • Everolimus
  • Exemestane
  • Ezogabine
  • Fentanyl
  • Fluvastatin
  • Gefitinib
  • Golimumab
  • Halothane
  • Hydrocodone
  • Ibrutinib
  • Idelalisib
  • Ifosfamide
  • Imatinib
  • Infliximab
  • Irinotecan
  • Irinotecan Liposome
  • Itraconazole
  • Ivabradine
  • Ivacaftor
  • Ixabepilone
  • Ixazomib
  • Ketoconazole
  • Lapatinib
  • Ledipasvir
  • Lidocaine
  • Linagliptin
  • Lopinavir
  • Macitentan
  • Magaldrate
  • Magnesium Carbonate
  • Magnesium Hydroxide
  • Magnesium Oxide
  • Magnesium Trisilicate
  • Methotrexate
  • Miconazole
  • Mifepristone
  • Naloxegol
  • Netupitant
  • Nifedipine
  • Nilotinib
  • Nimodipine
  • Nintedanib
  • Olaparib
  • Oritavancin
  • Orlistat
  • Osimertinib
  • Palbociclib
  • Panobinostat
  • Pazopanib
  • Perampanel
  • Pixantrone
  • Ponatinib
  • Posaonazole
  • Regorafenib
  • Reserpine
  • Rifampin
  • Rivaroxaban
  • Rocuronium
  • Roflumilast
  • Rolapitant
  • Romidepsin
  • Secukinumab
  • Sertraline
  • Siltuximab
  • Simeprevir
  • Sofosbuvir
  • Sonidegib
  • Sorafenib
  • St John's Wort
  • Sunitinib
  • Tacrolimus
  • Tamoxifen
  • Tasimelteon
  • Temsirolimus
  • Theophylline
  • Thiotepa
  • Ticagrelor
  • Tofacitinib
  • Tolvaptan
  • Trabectedin
  • Ulipristal
  • Vandetanib
  • Vemurafenib
  • Vilazodone
  • Vincristine
  • Vincristine Sulfate Liposome
  • Vinflunine
  • Vorapaxar
  • Voriconazole
  • Vortioxetine

Using this medication with any of the following medications may increase your risk of side effects. However, using both medications may be the best treatment for you.

If both medications are prescribed together, your doctor may change the dose or how often you take one or both medications:

  • Acetaminophen
  • Acetazolamide
  • Acyclovir
  • Amiodarone
  • Amitriptyline
  • Amprenavir
  • Atorvastatin
  • Betamethasone
  • Bexarotene
  • Bleomycin
  • Busulfan
  • Capecitabine
  • Carboplatin
  • Caspofungin
  • Chloramphenicol
  • Cimetidine
  • Ciprofloxacin
  • Cisplatin
  • Clobazam
  • Clofazimine
  • Clopidogrel
  • Colesevelam
  • Cortisone
  • Cyclosporine
  • Desogestrel
  • Dexamethasone
  • Dicumarol
  • Dienogest
  • Digitoxin
  • Diltiazem
  • Disopyramide
  • Disulfiram
  • Doxepin
  • Doxifluridine
  • Drospirenone
  • Estradiol Cypionate
  • Estradiol Valerate
  • Ethinyl Estradiol
  • Ethynodiol Diacetate
  • Etonogestrel
  • Felbamate
  • Fluconazole
  • Fludrocortisone
  • Fluorouracil
  • Fluoxetine
  • Fluvoxamine
  • Folic Acid
  • Fosamprenavir
  • Ginkgo
  • Imipramine
  • Isoniazid
  • Levodopa
  • Levomethadyl
  • Levonorgestrel
  • Levothyroxine
  • Medroxyprogesterone Acetate
  • Meperidine
  • Mestranol
  • Methoxsalen
  • Methsuximide
  • Midazolam
  • Nafimidone
  • Nelfinavir
  • Nilutamide
  • Nisoldipine
  • Norelgestromin
  • Norethindrone
  • Norgestimate
  • Norgestrel
  • Ospemifene
  • Oxcarbazepine
  • Paclitaxel
  • Pancuronium
  • Paroxetine
  • Phenprocoumon
  • Piperine
  • Prednisolone
  • Prednisone
  • Progabide
  • Quetiapine
  • Quinidine
  • Quinine
  • Remacemide
  • Rifapentine
  • Risperidone
  • Rufinamide
  • Sabeluzole
  • Shankhapulshpi
  • Simvastatin
  • Sirolimus
  • Sulfamethizole
  • Sulfamethoxazole
  • Sulfaphenazole
  • Sulthiame
  • Tegafur
  • Telithromycin
  • Tenidap
  • Tiagabine
  • Ticlopidine
  • Ticrynafen
  • Tirilazad
  • Tizanidine
  • Tolbutamide
  • Topiramate
  • Trazodone
  • Triamcinolone
  • Trimethoprim
  • Tubocurarine
  • Valacyclovir
  • Valproic Acid
  • Vecuronium
  • Verapamil
  • Vigabatrin
  • Viloxazine

Other Interactions: Certain medications should not be used while eating, or while eating certain foods in the case of negative interactions. Using alcohol or tobacco with certain medications may also cause negative interactions. Talk with your doctor about the use of your medication with food, alcohol or tobacco.

Using this medication with any of the following is not normally recommended, but may be unavoidable.

If used together, your doctor may change the dose or how often you take your medication or give you special instructions about the use of food, alcohol or tobacco:

  • Enteral Nutrition
  • Ethanol

Other Medical Problems: Pre-existing medical problems may affect the use of this medication.

Be sure to tell your doctor if you have any other medical problems, especially:

  • Bone problems (i.e. osteomalacia, osteoporosis)
  • Depression or mental illness
  • Diabetes
  • Lymphadenopathy (lymph node problems)
  • Porphyria (an enzyme problem)
  • Vitamin D deficiency - Use with caution. May make these conditions worse.
  • Hypoalbuminemia (low albumin in the blood)
  • Kidney disease
  • Liver disease - Use with caution. The effects may be increased because of slower removal from the body.

3 Proper Usage

Proper usage of Dilantin requires strict adherence to your doctor’s orders. Do not take more, less or for a longer or shorter period of time than your doctor tells you.

This medication comes with a patient information brochure. It is very important that your read this information. Ask your doctor if you have any questions.

This medication may be used along with other seizure medications. Do not stop taking any of your seizure medications unless your doctor tells you to.

Do not change brands or dosage forms of this medication without asking your doctor. Different products may not work the same way. Swallow the tablet whole or chew thoroughly before swallowing with a glass of water.

Measure the oral suspension with a marked measuring spoon, oral syringe or medication cup. If you are receiving tube-feeding preparations, it is best to take this medication before or after a feeding.

Dosing: Different patients will be given a different dose of this medication based on the strength of the medication. The number of doses you take each day, the time between doses and the length of time you take this medication depends on the reason you are taking this medication.

The following information only includes the average dose of this medication. If your dose is different, do not change it without first speaking to your doctor.

Extended-Release capsules:

  • Adults - Begin with 100mg 3 times a day or 300mg once per day. Your doctor may increase the dose as needed. For patients in a clinic or hospital, a loading dose of 1,000mg is divided into 3 doses (400mg, 300mg, 300mg) and given every 2 hours. Then normal dosing may begin 24 hours after the loading dose.
  • Teenagers and children over 6 years of age - 300mg per day. Your doctor may adjust the dose as needed.
  • Children 6 years of age and younger - Dose is based on body weight and must be determined by your doctor. Begin at 5mg per kilogram of body weight given in 2-3 doses per day.


  • Adults - Begin at 5mL or 1 teaspoon 3 times per day. Your doctor may adjust the dose as needed.
  • Teenagers and children over 6 years of age - 300mg per day. Your doctor may adjust the dose as needed.
  • Children 6 years of age and younger - Dose is based on body weight and must be determined by your doctor. Begin at 5mg per kilogram of body weight given in 2-3 doses per day.


  • Adults - 100mg 3 times per day. Your doctor may adjust the dose as needed.
  • Teenagers and children over 6 years of age - 300mg per day. Your doctor may adjust the dose as needed.
  • Children 6 years of age and younger - Dose is based on body weight and must be determined by your doctor. Begin at 5mg per kilogram of body weight given in 2-3 doses per day.

Missed dose: If you miss a dose of this medication, take it as soon as possible. If it is almost time for your next dose, skip the missed dose and resume your normal dosing schedule. Do not double dose.

Storage: Store this medication in a closed container at room temperature. Keep it away from heat, moisture, and direct light. Do not freeze.

Keep our of the reach of children. Do not keep expired medication or medication you no longer need. Ask your doctor how to dispose of any medication you do not use.

4 Precautions to Take

Before using Dilantin, there are some precautions you must take. It is very important that your doctor checks in with you often while you are receiving this medication to make sure that it is working properly.

Do not take other prescription or over-the-counter medications without asking your doctor. Using this medication while pregnant can harm your unborn child. Use an effective form of birth control to keep from getting pregnant. If you think you have become pregnant, inform your doctor immediately.

Do not use this medication if you are also using delavirdine. Using these medications together may cause unwanted effects.

Lymph node problems may occur while using this medication. Inform your doctor immediately if you have swollen, painful or tender lymph glands in your neck, armpit or groin.

Do not suddenly stop this medication without asking your doctor. They may want you to gradually reduce the amount that you use before stopping completely.

If you develop a skin rash, hives or any allergic reaction to this medication, inform your doctor immediately.

Inform your doctor immediately if you develop a fever, rash, swollen or painful lymph glands in the armpit, neck or groin, unusual bleeding or bruising or yellow skin or eyes (jaundice) after taking this medication. These may be symptoms of a life-threatening condition called Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS).

This medication may cause liver damage. Inform your doctor immediately if you have pain or tenderness in the upper stomach, pale stool, dark urine, loss of appetite, nausea, vomiting or yellow skin or eyes (jaundice).

This medication may temporarily lower the number of white blood cells in your blood, increasing the chance of infection. It can also lower the number of platelets, which are necessary for proper blood clotting.

If this occurs, there are certain precautions you can take to reduce the risk of infection or bleeding:

  • Take care to avoid people with infections. Call your doctor if you think you are getting an infection or if you get a fever or chills, cough or hoarseness, lower back or side pain or painful or difficult urination.
  • Inform your doctor immediately if you notice any unusual bleeding or bruising, black stool, blood in the urine or stool or red spots on your skin.
  • Take care when brushing or flossing your teeth. Your doctor or dentist may recommend other ways to clean your teeth and gums. Ask your doctor before having any dental work done.
  • Do not touch your eyes or the inside of your nose unless you have just washed your hands.
  • Take care when using sharp objects such as shaving razors or nail cutters and be sure not to cut yourself.
  • Avoid contact sports or other situations where bruising or injury may occur.

This medication may decrease bone mineral density. A low bone mineral density may cause weak bones or osteoporosis. If you have any questions, ask your doctor.

This medication may affect blood sugar levels. If you notice a change in the results of your blood or urine sugar tests or if you have any questions, ask your doctor.

This medication may cause some people to be agitated, irritable or display abnormal behaviours. It may also cause some people to have suicidal thoughts or tendencies or to become more depressed. If you notice any of these side-effects, inform your doctor immediately.

In some patients, normally younger patients, tenderness, swelling or bleeding of the gums (gingival hyperplasia) may appear soon after beginning treatment with this medication. To help prevent this, brush and floss your teeth carefully and regularly and massage your gums.

See your dentist every six months to have your teeth cleaned. If you have any questions or if you notice any tenderness, swelling or bleeding of your gums, inform your doctor or dentist.

Before you have any medical testing, inform the doctor in charge that you are taking that you are taking this medication. The results of some tests may be affected by this medication.

This medication may cause some people to become drowsy, have difficulty thinking or difficulty controlling movements. Make sure you know how you react to this medication before driving, using machinery or doing anything else that could be dangerous if you are not alert. Do not drink alcohol while taking this medication.

5 Potential Side Effects

As with many medications, there are several potential side effects associated with Dilantin. Although not all of these side-effects may occur, if they do occur they may need medical attention.

Check with your doctor immediately if you experience any of the following side-effects:

More common:

  • Decreased coordination
  • Mental confusion
  • Nervousness
  • Slurred speech
  • Trouble with breathing, speaking or swallowing
  • Unsteadiness, trembling, or other problems with muscle control or coordination


  • Inability to move the eyes
  • Increased blinking or spasms of the eyelid
  • Shakiness and unsteady walk shakiness in the legs, arms, hands, or feet
  • Sticking out of the tongue
  • Trembling or shaking of the hands or feet
  • Twitching, twisting, or uncontrolled repetitive movements of the tongue, lips, face, arms, or legs
  • Uncontrolled twisting movements of the neck, trunk, arms, or legs
  • Unusual facial expressions

Some side effects that may occur do not normally need medical attention. These may leave as your body becomes accustomed to treatment. Ask your doctor about ways to prevent or reduce some of these side effects.

Talk to your doctor if any of the following side effects continue or are bothersome, or if you have questions:

More common:

  • Difficulty sleeping (insomnia)
  • Uncontrolled eye movements

Some patients may experience other side effects that are not listed. Check with your doctor if you notice any other side effects. Ask your doctor for medical advice about side effects. You may report side effects to the FDA at 1-800-FDA-1088.

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