Phenytoin oral (patient information)
Why is this medication prescribed
Phenytoin is used to treat various types of convulsions and seizures. Phenytoin acts on the brain and nervous system in the treatment of epilepsy.
This medication is sometimes prescribed for other uses; ask your doctor or pharmacist for more information.
How should this medicine be used
Phenytoin comes as a capsule, extended-release (long-acting) capsule, chewable tablet, and liquid to take by mouth. It usually is taken two or three times a day. However, the extended-release capsules may be taken only once a day, usually at bedtime. Follow the directions on your prescription label carefully, and ask your doctor or pharmacist to explain any part you do not understand. Take phenytoin exactly as directed. Do not take more or less of it or take it more often than prescribed by your doctor.
Shake the liquid well before each use.
Do not open, crush, or chew the extended-release capsules; swallow them whole.
Continue to take phenytoin even if you feel well. Do not stop taking phenytoin without talking to your doctor, especially if you have taken large doses for a long time. Abruptly stopping the drug can cause seizures. Your doctor probably will decrease your dose gradually.
Other uses for this medicine
Phenytoin is also used to control arrhythmias (irregular heartbeat) and to treat migraine headaches and facial nerve pain.
Talk to your doctor about the possible risks of using this drug for your condition.
What special precautions should I follow
Before taking phenytoin:
- tell your doctor and pharmacist if you are allergic to phenytoin or any other drugs.
- tell your doctor and pharmacist what prescription and nonprescription medications you are taking, especially other seizure medications, acetaminophen (Tylenol), antacids such as Mylanta or Maalox, anticoagulants ('blood thinners') such as warfarin (Coumadin), chloramphenicol (Chloromycetin), cimetidine (Tagamet), disopyramide (Norpace), doxycycline (Vibramycin), fluconazole (Diflucan), heart medications such as digoxin, ibuprofen (Advil), isoniazid (INH), lithium, medications for anxiety such as diazepam (Valium), medications for colds or allergies such as chlorpheniramine (Chlor-Trimeton), medications for depression such as amitriptyline (Elavil), meperidine (Demerol), omeprazole (Prilosec), oral contraceptives, pyridoxine (vitamin B6), quinidine, rifampin, sedatives such as phenobarbital, sucralfate (Carafate), theophylline (Theo-Dur), tranquilizers such as chlorpromazine (Thorazine), and other vitamins. Phenytoin affects the action of other medications, and many medications can affect the action of phenytoin. Tell your doctor and pharmacist everything you are taking.
- tell your doctor if you have or have ever had irregular heartbeat; low blood pressure; problems with your blood sugar; a blood disorder; or heart, kidney, or liver disease.
- tell your doctor if you are pregnant, plan to become pregnant, or are breast-feeding. If you become pregnant while taking phenytoin, call your doctor.
- if you are having surgery, including dental surgery, tell the doctor or dentist that you are taking phenytoin.
- you should know that this drug may make you drowsy. Do not drive a car or operate machinery until you know how this drug affects you.
- remember that alcohol can add to the drowsiness caused by this drug.
What special dietary instructions should I follow
Phenytoin may cause an upset stomach. Take phenytoin with food. If you are on enteral feeding, it is best to take phenytoin 2 hours before or after the enteral feeding. Drink plenty of water when taking this medicine.
What should I do if I forget a dose
Take the missed dose as soon as you remember it. However, if it is almost time for the next dose, skip the missed dose and continue your regular dosing schedule. Do not take a double dose to make up for a missed one.
Side effects
Mild side effects
Side effects from phenytoin may occur. Tell your doctor if any of these symptoms are severe or do not go away:
- drowsiness
- redness, irritation, bleeding, and swelling of the gums
- upset stomach
- vomiting
- constipation
- stomach pain
- loss of taste and appetite
- weight loss
- difficulty swallowing
- mental confusion
- blurred or double vision
- insomnia
- nervousness
- muscle twitching
- headache
- increased hair growth
Severe side effects
If you experience any of the following symptoms, call your doctor immediately:
- difficulty coordinating movements
- skin rash
- easy bruising
- tiny purple-colored skin spots
- bloody nose
- slurred speech
- unusual bleeding
- yellowing of the skin or eyes
- dark urine
- swollen glands
- fever
- sore throat
If you experience a serious side effect, you or your doctor may send a report to the Food and Drug Administration's (FDA) MedWatch Adverse Event Reporting program online [at http://www.fda.gov/MedWatch/report.htm] or by phone [1-800-332-1088].
What storage conditions are needed for this medicine
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature, away from excess heat and moisture (not in the bathroom). Protect the extended-release capsules and liquid from light. Do not freeze the liquid. Throw away any medication that is outdated or no longer needed. Talk to your pharmacist about the proper disposal of your medication.
In case of emergency/overdose
In case of overdose, call your local poison control center at 1-800-222-1222. If the victim has collapsed or is not breathing, call local emergency services at 911.
What other information should I know
Keep all appointments with your doctor and the laboratory. Your doctor will order certain lab tests to check your response to phenytoin.
Phenytoin capsules and tablets (and different brands of phenytoin) have different effects. Do not change brands of phenytoin without talking to your doctor.
Call your doctor if you continue to have seizures or convulsions while taking this medication.
If you give this drug to a child, observe and keep a record of the child's moods, behavior, attention span, hand-eye coordination, and ability to solve problems and perform tasks requiring thought. Ask the child's teacher to keep a similar record. This information can help the child's doctor determine whether to continue the drug or to change the dose or drug.
Wear identification (Medic Alert) indicating medication use and epilepsy.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
Brand names
- Dilantin®
- Dilantin® Infatabs®
- Dilantin® Kapseals®
- Dilantin-125®
- Phenytek®