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.

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.
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 discuss with my healthcare provider before taking Phenytoin?

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:

• liver disease
• porphyria
• diabetes; or
• a vitamin D deficiency or any other condition that causes thinning of the bones

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 affect your blood sugar. If you are a diabetic, check your blood sugar regularly while you are taking this medication.
FDA pregnancy category D. Do not use phenytoin without your doctor’s consent if you are pregnant. It could harm the unborn baby. Phenytoin may also not be as effective in reducing seizures if taken during pregnancy. Use effective birth control, and tell your doctor if you become pregnant during treatment.
Although phenytoin might harm an unborn baby, having a seizure during pregnancy could harm both mother and baby. Follow your doctor’s instructions about taking phenytoin while you are pregnant.
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.

Phenytoin Side Effects

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 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.

Phenytoin Interactions

What other drugs 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

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:

• phenobarbital (Luminal, Solfoton), valproic acid (Depakene) or divalproex sodium (Depakote)
• 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 medications you use. This includes prescription, over-the-counter, vitamin, and herbal products. Do not start a new medication without telling your doctor. Keep a list of all your medicines and show it to any healthcare provider who treats you.

What should I avoid while taking Phenytoin?

Drinking alcohol 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 may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert.

Phenytoin Dosage

How should I take Phenytoin?

Take exactly as prescribed by your doctor. Do not take in larger or smaller amounts or for longer than recommended. Follow the directions on your prescription label.
Do not crush, chew, break, or open an extended-release capsule. Swallow it whole. Breaking or opening the pill may 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. Measure the liquid with a special dose-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 often. You may also need a blood test when switching from one form of phenytoin to another. Visit your doctor regularly.
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.
Wear a medical alert tag or carry an ID card stating that you take phenytoin. Any medical care provider who treats you should know that you are taking a seizure medication.
Store at room temperature away from moisture, light, and heat.

What happens if I overdose on Phenytoin?

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. 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.

What happens if I miss a dose of Phenytoin?

Take the missed dose as soon as you remember. Skip the missed dose if it is almost time for your next scheduled dose. Do not take extra medicine to make up the missed dose.
Sourced from everydayhealth.com