• Basic Info
• Top Questions
• Clinical Info
• Interactions

What is phenytoin?
Phenytoin is an anti-epileptic drug, also called an anticonvulsant. It works by slowing down impulses in the brain that cause seizures. Phenytoin is used to control seizures. Phenytoin is not made to treat all types of seizures, and your doctor will determine if it is the right medication for you. Phenytoin may also be used for other purposes not listed in this medication guide.

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What is the price of this medication and similar alternatives?

This pricing information is subject to change at the sole discretion of DS Pharmacy. For the most current and up-to-date pricing information, please visit drugstore.com.

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What are the possible side effects of phenytoin?

Get emergency medical help if you have any of these signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Call your doctor at once if you have any of these serious side effects:

• swollen glands;

• fever, sore throat, and headache with a severe blistering, peeling, and red skin rash;

• confusion, hallucinations, unusual thoughts or behavior;

• slurred speech, loss of balance or coordination;

• restless muscle movements in your eyes, tongue, jaw, or neck;

• tremor (uncontrolled shaking);

• extreme thirst or hunger, urinating more than usual;

• nausea, stomach pain, low fever, loss of appetite, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes);

• easy bruising or bleeding;

• swollen or tender gums; or

• changes in the shape of your face or lips.

Less serious side effects may include:

• mild skin rash or itching;

• dizziness, nervousness, sleep problems (insomnia);

• twitching;

• nausea, vomiting, constipation;

• headache; or

• joint pain.

This is not a complete list of side effects and others may occur. Tell your doctor about any unusual or bothersome side effect.

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How should I take phenytoin?
Take this medication exactly as it was prescribed for you. Do not take the medication in larger amounts, or take it for longer than recommended by your doctor. Follow the directions on your prescription label. Do not crush, chew, break, or open an extended-release capsule. Swallow the pill whole. It is specially made to release medicine slowly in the body. Breaking or opening the pill would cause too much of the drug to be released at one time. Do not use any phenytoin capsule or tablet that has changed colors. Call your doctor for a new prescription.

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What is the most important information I should know about phenytoin?
If you are taking phenytoin to prevent seizures, keep taking the medication even if you feel fine. You may have an increase in seizures if you stop taking phenytoin. Follow your doctor's instructions. Do not change your dose of phenytoin without your doctor's advice. Tell your doctor if the medication does not seem to work as well in treating your condition. Carry an ID card or wear a medical alert bracelet stating that you are taking phenytoin, in case of emergency. Any doctor, dentist, or emergency medical care provider who treats you should know that you are taking a seizure medication.

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What happens if I miss a dose?
Take the missed dose as soon as you remember. If it is almost time for your next dose, skip the missed dose and take the medicine at your next regularly scheduled time. Do not take extra medicine to make up the missed dose.

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What other drugs will affect phenytoin?
Drugs that can increase phenytoin levels in your blood include: stomach acid reducers such as cimetidine (Tagamet), ranitidine (Zantac), famotidine (Pepcid), or nizatidine (Axid); certain sedatives (such as Librium or Valium) or antidepressants (such as Prozac); estrogen hormone replacement; chlorpromazine (Thorazine), prochlorperazine (Compazine), thioridazine (Mellaril) and other phenothiazines; disulfiram (Antabuse); methylphenidate (Ritalin, Concerta, Daytrana); and sulfa drugs such as Septra or Bactrim.

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Can I take this if I am pregnant or trying to get pregnant or if I am breastfeeding?

Phenytoin has not been formally assigned to a pregnancy category. An increased risk of congenital malformations has been associated with the use of anticonvulsants agents (including phenytoin) in epileptic women during pregnancy. Anomalies associated with anticonvulsant use in pregnancy include neural tube defects, cleft lips, cleft palates, cardiac defects, and microcephaly. A specific "fetal hydantoin syndrome" involving a number of abnormalities has been described. Neonatal coagulation defects have also been reported in infants whose mothers took phenytoin during pregnancy. Vitamin K administered to the mother before delivery and to the neonate has been reported to reduce this defect. Phenytoin may cause folate deficiency. Some clinicians have recommended early maternal monitoring of folate levels and administration of folic acid when appropriate. There are no controlled data in human pregnancy. Phenytoin should only be given during pregnancy when there are no alternatives and benefit outweighs risk.

Features of the fetal hydantoin syndrome include both craniofacial and distal limb abnormalities. The specific facial features include a broad nasal bridge, wide fontanel, epicanthic folds, short upturned nose, hypertelorism, ocular abnormalities, prominent and low set ears, wide mouth, cleft lip or palate, prominent lips and variations in the size and shape of the head. The specific distal limb abnormalities include hypoplasia of the distal phalanges, finger-like thumbs, small or absent nails, and altered palmar creases. A variety of tumors (including neuroblastoma) have also been reported in the offspring of women taking phenytoin. Recent studies have suggested that in utero exposure to phenytoin may result in significantly lower IQ scores. Some clinicians have recommended that the need for anticonvulsant therapy be reevaluated prior to pregnancy if possible. If a need is clearly present, consideration may be given to the use of alternative anticonvulsants (such as carbamazepine) which may pose a smaller risk. If phenytoin therapy is deemed necessary, close observation for clinical and laboratory evidence of altered phenytoin effect is indicated throughout the course of pregnancy. Pregnancy results in a number of changes in the pharmacokinetic disposition of phenytoin. The plasma clearance is increased (with a peak just before or in the first weeks after delivery). The plasma protein binding is decreased. Some of the changes in the pharmacokinetic disposition of phenytoin may be related to increases in the hepatic metabolism of the drug. Some women who must take phenytoin during pregnancy may require dose increases in order to maintain seizure control. Physicians are encouraged to register patients before fetal outcome is known (e.g., ultrasound, results of amniocentesis, etc) into the Antiepileptic Drug (AED) Pregnancy Registry at 1-888-233-2334 or 1-888-AED-AED4. This is an ongoing study at the Massachusetts General Hospital/Harvard Medical School. This study is designed to monitor the outcomes of pregnant women exposed to antiepileptic drugs in order to determine which therapies are associated with increased risk.

Phenytoin is excreted into human milk in small amounts. Typical doses given to a nursing mother would be expected to result in very small infant doses (less than 5% of a typical dose for most infants). The American Academy of Pediatrics classifies phenytoin as a drug which is "usually compatible with breast-feeding." The Academy notes one case of methemoglobinemia as a cause of possible concern.

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Who should NOT use this medication?

• IV use contraindicated in patients with sinus bradycardia, SA block, second- or third-degree AV block, or Adams-Stokes syndrome.
• Known hypersensitivity to phenytoin or any ingredient in the respective formulation or to other hydantoins.

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What happens if I overdose?
Seek emergency medical attention if you think you have used too much of this medicine. An overdose of phenytoin can be fatal. Overdose symptoms may include twitching eye movements, slurred speech, loss of balance, tremor, muscle stiffness or weakness, nausea, vomiting, feeling light-headed, fainting, and slow or shallow breathing.

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What should I discuss with my healthcare provider before taking phenytoin?
Do not use this medication if you are allergic to phenytoin. Before taking this medication, tell your doctor if you are allergic to any drugs, or if you have: liver disease; porphyria; diabetes; or a vitamin D deficiency or any other condition that causes thinning of the bones. If you have any of these conditions, you may need a dose adjustment or special tests to safely take this medication. Phenytoin can lower your blood sugar. If you are a diabetic, check your blood sugar regularly while you are taking this medication.

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Can I stop taking the medication if I feel better?
As a general rule, you should always take your medications exactly as prescribed and do not change the dosage or stop taking the medication without first discussing it with your healthcare provider.

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I am on so many medications; do I have to take them all?
This is called polypharmacy—many different medications being used at the same time by one person. Sometimes, being on multiple medications is acceptable and appropriate but at other times it may be problematic. If you are receiving your medications from multiple physicians you need to ensure that they all know what medications you are taking. The best way to do this is to make a list of all the medications you are currently using, including all nutritional supplements, homeopathic remedies, vitamins and over-the-counter drugs (if possible, also include all the diseases you have been diagnosed with). Give a copy to every doctor who takes care of you so they have it on file, this way they can avoid duplicating medications and perhaps even try to consolidate some. After every doctor's visit remember to update the list accordingly. Also, as much as you possibly can, try to use the same pharmacy to fill all your prescriptions, this way any potential drug interactions can be caught and averted.

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Where can I get more information?
More Information

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