What is phenytoin (oral)?
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.
What should I discuss with my healthcare provider before taking phenytoin (oral)?
You should not use this medication if you are allergic to phenytoin.
If you have any of these other conditions, you may need a dose adjustment or special tests to
safely use this medication:
You may have thoughts about suicide while taking this medication. Tell your
doctor if you have new or worsening depression or suicidal thoughts during the first several months of
treatment, or whenever your dose is changed.
Your family or other caregivers should also be alert to changes in your mood or symptoms.
Your doctor will need to check you at regular visits. Do not miss any scheduled appointments.
Patients of Asian ancestry may have a higher risk of developing a rare but serious skin reaction
to phenytoin. Your doctor may recommend a blood test before you start the medication to determine
your risk of this skin reaction.
Phenytoin can lower your blood sugar. If you are a diabetic, check your blood sugar regularly
while you are taking this medication.
FDA pregnancy category D. This medication can cause harm to an unborn baby.
Phenytoin may also not be as effective in reducing seizures if taken during pregnancy. Do not use
phenytoin without your doctor's consent if you are pregnant. Tell your doctor if you become pregnant
during treatment. Use an effective form of birth control while you are using this medication.
Phenytoin can make birth control pills less effective. Use a non-hormonal form of birth control
(such as a condom or diaphragm with spermicide) to prevent an unintended pregnancy.
Phenytoin can pass into breast milk and may harm a nursing baby. Do not use this
medication without telling your doctor if you are breast-feeding a baby.
How should I take phenytoin (oral)?
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.
The chewable tablet may be chewed, broken, or crushed before swallowing, or it may be
swallowed whole.
Shake the oral suspension (liquid) well just before you measure a dose. To be sure you get
the correct dose, measure the liquid with a marked measuring spoon or medicine cup, not with a regular
table spoon. If you do not have a dose-measuring device, ask your pharmacist for one.
To be sure this medication is helping your condition, your blood may need to be tested on a
regular basis. You may also need a blood test when switching from one form of phenytoin to another.
Do not miss any scheduled appointments.
If you are taking phenytoin to treat 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.
Store phenytoin at room temperature away from moisture, light, and heat.
What happens if I miss a dose of phenytoin (oral)?
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.
Where can I get more information about phenytoin (oral)?
Your pharmacist has information about phenytoin (oral) written for health professionals that you may read.
What are the possible side effects of phenytoin (oral)?
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 new or worsening symptoms such as: mood or
behavior changes, depression, anxiety, or if you feel agitated, hostile, restless, hyperactive (mentally or
physically), or have thoughts about suicide or hurting yourself.
Call your doctor at once if you have any of these serious side effects:
-
swollen glands, easy bruising or bleeding;, swollen or tender gums;
-
fever, sore throat, and headache with a severe blistering,
peeling, and red skin rash;
-
the first sign of any skin rash, no matter how mild;
-
confusion, hallucinations, unusual thoughts or behavior;
-
slurred speech, loss of balance or coordination;
-
tremor (uncontrolled shaking), restless muscle movements
in your eyes, tongue, jaw, or neck;
-
extreme thirst or hunger, urinating more than usual;
-
loss of appetite, dark urine, clay-colored stools, jaundice
(yellowing of the skin or eyes); 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);
-
nausea, vomiting, constipation; or
-
headache, joint pain.
This is not a complete list of side effects and others may occur. Call your
doctor for medical advice about side effects. You may report side effects to FDA at
1-800-FDA-1088.
What is the most important information I should know about phenytoin (oral)?
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.
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.
You may have thoughts about suicide while taking this medication. Your doctor will need to
check you at regular visits. Do not miss any scheduled appointments.
Call your doctor at once if you have any new or worsening symptoms such as: mood or
behavior changes, depression, anxiety, or if you feel agitated, hostile, restless, hyperactive (mentally or
physically), or have thoughts about suicide or hurting yourself.
What should I avoid while taking phenytoin (oral)?
Avoid drinking alcohol. It can increase some of the side effects of phenytoin, and can also
increase your risk of seizure.
Avoid taking antacids at the same time you take phenytoin. Antacids can make it harder for
your body to absorb the medication.
Phenytoin can cause side effects that may impair your thinking or reactions. Be careful if
you drive or do anything that requires you to be awake and alert.
What other drugs will affect phenytoin (oral)?
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.
Drugs that
can make phenytoin less effective in controlling
seizures
include carbamazepine (Tegretol, Epitol, Carbatrol), sucralfate (Carafate), and
molindone (Moban).
Other drugs that can interact with phenytoin include:
-
steroid medicines (prednisone and others);
-
antidepressants such as amitriptyline (Elavil), clomipramine
(Anafranil), imipramine (Janimine, Tofranil), paroxetine (Paxil), and others;
-
antibiotics such as rifampin (Rimactane, Rifadin, Rifamate)
or doxycycline (Doryx, Vibramycin, Adoxa, and others);
-
digoxin (digitalis, Lanoxin), furosemide (Lasix); and
-
theophylline (Elixophyllin, Theo-Dur, Theo-Bid, Theolair,
Uniphyl).
This list is not complete and there are many other
medicines that can interact with phenytoin.
Tell your doctor about all the prescription and
over-the-counter medications you use. This includes vitamins, minerals, herbal products, and drugs
prescribed by other doctors. Do not start using a new medication without telling your doctor. Keep a
list with you of all the medicines you use and show this list to any doctor or other healthcare provider
who treats you.
What happens if I have an overdose of phenytoin (oral)?
