Phenytoin is used to control certain type of seizures, and to treat and prevent seizures that may begin during or after surgery to the brain or nervous system. Phenytoin is in a class of medications called anticonvulsants. It works by decreasing abnormal electrical activity in the brain.
Phenytoin comes as an extended-release (long-acting) capsule, a chewable tablet, and a suspension (liquid) to take by mouth. The chewable tablet and suspension are usually taken two or three times a day. The extended-release capsules are usually taken 1-4 times a day. Take phenytoin at around the same time(s) every day. 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.
Your doctor will start you on a low dose of phenytoin and gradually increase your dose, not more often than once every 7-10 days.
Different phenytoin products are absorbed by the body in different ways and cannot be substituted for one another. If you need to switch from one phenytoin product to another, your doctor may need to adjust your dose. Each time you receive your medication, check to be sure that you have received the phenytoin product that was prescribed for you. Ask your pharmacist if you have are not sure that you received the right medication.
Shake the liquid well before each use to mix the medication evenly. Use an accurate measuring device to be sure you receive the correct amount of medication. Ask your doctor or pharmacist if you have any questions about how to measure your dose.
Swallow the extended-release capsules whole; do not split, chew, or crush them. Do not take capsules that are discolored.
You may chew the chewable tablets thoroughly before swallowing them, or you may swallow them whole without chewing.
If you are receiving formula or supplements through a feeding tube, talk to your doctor about when you should take phenytoin. You will need to allow some time between receiving your feedings and taking phenytoin.
Phenytoin may help control your condition but will not cure it. Continue to take phenytoin even if you feel well. Do not stop taking phenytoin without talking to your doctor, even if you experience side effects such as unusual changes in behavior or mood. If you suddenly stop taking phenytoin, your seizures may worsen. Your doctor will probably decrease your dose gradually.
Phenytoin is also used to control irregular heartbeat. Talk to your doctor about the risks of using this medication for your condition.
This medication may be prescribed for other uses; ask your doctor or pharmacist for more information.
Before taking phenytoin,
Unless your doctor tells you otherwise, continue your normal diet.
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.
Phenytoin may cause an increase in your blood sugar. Talk to your doctor about the symptoms of high blood sugar and what to do if you experience these symptoms.
Phenytoin may cause side effects. Tell your doctor if any of these symptoms are severe or do not go away:
Some side effects can be serious. If you experience any of the following symptoms, call your doctor immediately:
Phenytoin may cause other side effects. Call your doctor if you have any unusual problems while you are taking this medication.
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 Web Site] or by phone [1-800-332-1088].
Taking phenytoin may increase the risk that you will develop osteomalacia (weakening and softening of the bones) and problems with your lymph nodes including Hodgkin's disease (cancer that begins in the lymph system). Talk to your doctor about the risks of using this medication to treat your condition.
Keep this medication in the container it came in, tightly closed, and out of reach of children. Store it at room temperature, away from light and excess heat and moisture (not in the bathroom). 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 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.
Symptoms of overdose may include:
Keep all appointments with your doctor and the laboratory. Your doctor may order certain lab tests to check your response to phenytoin.
Before having any laboratory test, tell your doctor and the laboratory personnel that you are taking phenytoin.
Do not let anyone else take your medication. Ask your pharmacist any questions you have about refilling your prescription.
It is important for you to keep a written list of all of the prescription and nonprescription (over-the-counter) medicines you are taking, as well as any products such as vitamins, minerals, or other dietary supplements. You should bring this list with you each time you visit a doctor or if you are admitted to a hospital. It is also important information to carry with you in case of emergencies.
AHFS® Consumer Medication Information. © Copyright, The American Society of Health-System Pharmacists, Inc., 7272 Wisconsin Avenue, Bethesda, Maryland. All Rights Reserved. Duplication for commercial use must be authorized by ASHP.
Selected Revisions: May 1, 2009.