Adult Medication

Brand Names: US

Dilantin; Dilantin Infatabs; Phenytek; Phenytoin Infatabs

Brand Names: Canada

Dilantin; Novo-Phenytoin; Taro-Phenytoin; Tremytoine Inj



  • This drug may cause a heartbeat that is not normal or low blood pressure if given too fast. Your doctor will watch your heart closely when you get this drug.

What is this drug used for?

  • It is used to help control certain kinds of seizures.
  • It may be given to you for other reasons. Talk with the doctor.

What do I need to tell my doctor BEFORE I take this drug?

All products:

  • If you have an allergy to phenytoin or any other part of this drug.
  • If you are allergic to any drugs like this one, any other drugs, foods, or other substances. Tell your doctor about the allergy and what signs you had, like rash; hives; itching; shortness of breath; wheezing; cough; swelling of face, lips, tongue, or throat; or any other signs.
  • If you are taking delavirdine.
  • If you are breast-feeding. Do not breast-feed while you take this drug.


  • If you have heart problems.
This is not a list of all drugs or health problems that interact with this drug.
Tell your doctor and pharmacist about all of your drugs (prescription or OTC, natural products, vitamins) and health problems. You must check to make sure that it is safe for you to take this drug with all of your drugs and health problems. Do not start, stop, or change the dose of any drug without checking with your doctor.

What are some things I need to know or do while I take this drug?

  • Tell all of your health care providers that you take this drug. This includes your doctors, nurses, pharmacists, and dentists.
  • Avoid driving and doing other tasks or actions that call for you to be alert until you see how this drug affects you.
  • This drug interacts with many other drugs. The chance of this drug’s side effects may be raised or how well this drug works may be lowered. The chance of the other drugs’ side effects may also be raised. This may include very bad, life-threatening, or deadly side effects. Check with your doctor and pharmacist to make sure that it is safe for you to take this drug with all of your other drugs (prescription or OTC, natural products, vitamins).
  • Very bad and sometimes deadly skin reactions (Stevens-Johnson syndrome/toxic epidermal necrolysis) have happened with this drug. People of Asian descent are most likely to get these. Get medical help right away if you have signs like red, swollen, blistered, or peeling skin (with or without fever); red or irritated eyes; or sores in your mouth, throat, nose, or eyes.
  • Patients who take this drug may be at a greater risk of having thoughts or actions of suicide. The risk may be greater in people who have had these thoughts or actions in the past. Call the doctor right away if signs like low mood (depression), nervousness, restlessness, grouchiness, panic attacks, or changes in mood or actions are new or worse. Call the doctor right away if any thoughts or actions of suicide occur.
  • Lymph node problems like cancer have happened in people taking this drug. It is not known if this drug may be the cause. Talk with your doctor if you have swollen glands.
  • Have blood work checked as you have been told by the doctor. Talk with the doctor.
  • Have the level of phenytoin in your blood checked as you have been told by your doctor. If the level is too high, some side effects may happen. This includes a type of brain problem that may not go back to normal. Talk with your doctor.
  • This drug may affect certain lab tests. Tell all of your health care providers and lab workers that you take this drug.
  • If you have high blood sugar (diabetes), you will need to watch your blood sugar closely. Tell your doctor if you get signs of high blood sugar like confusion, feeling sleepy, more thirst, more hungry, passing urine more often, flushing, fast breathing, or breath that smells like fruit.
  • Talk with your doctor before you drink alcohol or use other drugs and natural products that slow your actions.
  • If you are 65 or older, use this drug with care. You could have more side effects.
  • Birth control pills and other hormone-based birth control may not work as well to prevent pregnancy. Use some other kind of birth control also like a condom when taking this drug.
  • This drug may cause harm to the unborn baby if you take it while you are pregnant. If you are pregnant or you get pregnant while taking this drug, call your doctor right away.

What are some side effects that I need to call my doctor about right away?

WARNING/CAUTION: Even though it may be rare, some people may have very bad and sometimes deadly side effects when taking a drug. Tell your doctor or get medical help right away if you have any of the following signs or symptoms that may be related to a very bad side effect:

All products:

  • Signs of an allergic reaction, like rash; hives; itching; red, swollen, blistered, or peeling skin with or without fever; wheezing; tightness in the chest or throat; trouble breathing or talking; unusual hoarseness; or swelling of the mouth, face, lips, tongue, or throat.
  • Change in balance.
  • Trouble walking.
  • Feeling confused.
  • Slurred speech.
  • Swollen or sore gums.
  • Very bad muscle pain.
  • Trouble controlling body movements.
  • If seizures are worse or not the same after starting this drug.
  • A burning, numbness, or tingling feeling that is not normal.
  • Weak bones with long-term use.
  • Bone pain.
  • Not able to control eye movements.
  • Shakiness.
  • A very bad and sometimes deadly effect has happened in people taking drugs for seizures like this drug. Call your doctor right away if you have swollen glands; fever; rash; chest pain; unable to pass urine or change in the amount of urine passed; or signs of liver problems like dark urine, feeling tired, not hungry, upset stomach or stomach pain, light-colored stools, throwing up, or yellow skin or eyes.
  • Rarely, certain blood problems have happened with this drug. This can lead to bleeding problems or infections. Sometimes, these have been deadly. Tell your doctor right away if you have signs of infection like fever, chills, very bad sore throat, ear or sinus pain, cough, more sputum or change in color of sputum, pain with passing urine, mouth sores, or a wound that will not heal. Tell your doctor right away if you have any unexplained bruising or bleeding, or if you feel very tired or weak.


  • A fast heartbeat.
  • Slow heartbeat.
  • A heartbeat that does not feel normal.
  • Pain where the shot was given.
  • Redness or swelling where the shot is given.
  • Change in skin color to black or purple.

What are some other side effects of this drug?

All drugs may cause side effects. However, many people have no side effects or only have minor side effects. Call your doctor or get medical help if any of these side effects or any other side effects bother you or do not go away:
  • Dizziness.
  • Feeling sleepy.
  • Headache.
  • Feeling nervous and excitable.
  • Not able to sleep.
  • Hard stools (constipation).
  • Upset stomach or throwing up.
These are not all of the side effects that may occur. If you have questions about side effects, call your doctor. Call your doctor for medical advice about side effects.
You may report side effects to your national health agency.

How is this drug best taken?

Use this drug as ordered by your doctor. Read all information given to you. Follow all instructions closely.

All oral products:

  • Take with or without food. Take with food if it causes an upset stomach.
  • Take this drug at the same time of day.
  • To gain the most benefit, do not miss doses.
  • Keep taking this drug as you have been told by your doctor or other health care provider, even if you feel well.
  • Do not stop taking this drug all of a sudden without calling your doctor. You may have a greater risk of seizures. If you need to stop this drug, you will want to slowly stop it as ordered by your doctor.
  • If this drug is given through a feeding tube, stop tube feeding for 2 hours before giving this drug. Restart tube feeding 2 hours after giving.

Long-acting capsules:

  • Swallow whole. Do not chew, break, or crush.
  • Do not take if product changes color.

Chewable tablet:

  • Chew or swallow tablet whole.


  • Shake well before use.
  • Measure liquid doses carefully. Use the measuring device that comes with this drug. If there is none, ask the pharmacist for a device to measure this drug.


  • It is given as a shot into a vein.

All products:

  • Wear disease medical alert ID (identification).
  • Follow laws about driving with a seizure problem.
  • Do not switch brands or types of this drug (like tablets, liquid) unless you talk with the doctor. They may not work the same.
  • Take good care of your teeth. See a dentist often.

What do I do if I miss a dose?

All oral products:

  • Take a missed dose as soon as you think about it.
  • If it is close to the time for your next dose, skip the missed dose and go back to your normal time.
  • Do not take 2 doses at the same time or extra doses.


  • Call your doctor to find out what to do.

How do I store and/or throw out this drug?

All oral products:

  • Store at room temperature.
  • Protect from light.
  • Store in a dry place. Do not store in a bathroom.


  • Do not freeze.


  • If you need to store this drug at home, talk with your doctor, nurse, or pharmacist about how to store it.

All products:

  • Keep all drugs in a safe place. Keep all drugs out of the reach of children and pets.
  • Check with your pharmacist about how to throw out unused drugs.

General drug facts

  • If your symptoms or health problems do not get better or if they become worse, call your doctor.
  • Do not share your drugs with others and do not take anyone else’s drugs.
  • Keep a list of all your drugs (prescription, natural products, vitamins, OTC) with you. Give this list to your doctor.
  • Talk with the doctor before starting any new drug, including prescription or OTC, natural products, or vitamins.
  • Some drugs may have another patient information leaflet. If you have any questions about this drug, please talk with your doctor, nurse, pharmacist, or other health care provider.
  • If you think there has been an overdose, call your poison control center or get medical care right away. Be ready to tell or show what was taken, how much, and when it happened.

Consumer Information Use and Disclaimer

This information should not be used to decide whether or not to take this medicine or any other medicine. Only the healthcare provider has the knowledge and training to decide which medicines are right for a specific patient. This information does not endorse any medicine as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this medicine. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this medicine. This information is not specific medical advice and does not replace information you receive from the healthcare provider. You must talk with the healthcare provider for complete information about the risks and benefits of using this medicine.

Last Reviewed Date



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