Phenytoin: Uses & Side Effects

Phenytoin, an anti-epileptic drug, also called an anticonvulsant,works by slowing down impulses in the brain that cause seizures. phenytoin does not treat all types of seizures, and your doctor will determine if it is the right medicine for you.

Precautions of phenytoin

You should not use phenytoin if you are allergic to it, or if you have ever had:

  • liver problems caused by phenytoin;
  • an allergy to similar medicines such as ethotoin, fosphenytoin, or mephenytoin; or
  • if you currently take delavirdine (Rescriptor).

To make sure phenytoin is safe for you, tell your doctor if you have ever had:

  • heart problems;
  • liver disease;
  • diabetes;
  • depression;
  • suicidal thoughts or actions;
  • a vitamin D deficiency or any other condition that causes thinning of the bones;
  • porphyria (a genetic enzyme disorder that causes symptoms affecting the skin or nervous system); or
  • if you are of Asian ancestry (you may need a special blood test to determine your risk for having a skin reaction to this medicine).

Some people have thoughts about suicide while taking this medicine. Your doctor will need to check your progress at regular visits. Your family or other caregivers should also be alert to changes in your mood or symptoms.

Seizure control is very important during pregnancy. Do not start or stop taking phenytoin without your doctor’s advice if you are pregnant. Phenytoin may harm an unborn baby, but having a seizure during pregnancy could harm both mother and baby. Tell your doctor right away if you become pregnant while taking this medicine.

If you are pregnant, your name may be listed on a pregnancy registry to track the effects of phenytoin on the baby.

If you have taken this medicine during pregnancy, be sure to tell the doctor who delivers your baby about your phenytoin use. Both you and the baby may need to receive medications to prevent excessive bleeding during delivery and just after birth.

Phenytoin can make birth control pills less effective. Ask your doctor about using a non-hormonal birth control (condom, diaphragm with spermicide) to prevent pregnancy.

It may not be safe to breast-feed while using this medicine. Ask your doctor about any risk.

Uses of phenytoin

Take phenytoin exactly as prescribed by your doctor. Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose.

Swallow an extended-release capsule whole and do not crush, chew, break, or open it.

Phenytoin chewable tablets are not for once-per-day dosing. You must take them 2 or 3 times per day. Follow your doctor’s dosing instructions very carefully.

Shake the oral suspension (liquid) before you measure a dose. Use the dosing syringe provided, or use a medicine dose-measuring device (not a kitchen spoon).

You may need frequent blood tests. You may also need a blood test when switching from one form to another. Visit your doctor regularly.

Tell your doctor if phenytoin does not seem to work as well in controlling your seizures. Do not stop using this medicine suddenly, even if you feel fine. Stopping suddenly may cause increased seizures. Follow your doctor’s instructions about tapering your dose.

In case of emergency, wear or carry medical identification to let others know you have seizures.

Phenytoin can cause swelling in your gums. Brush and floss your teeth and visit your dentist regularly to help prevent this problem.

Store at room temperature away from moisture, light, and heat.

Side effects of phenytoin

Get emergency medical help if you have signs of an allergic reaction to phenytoin (hives, difficult breathing, swelling in your face or throat) or a severe skin reaction (fever, sore throat, burning in your eyes, skin pain, red or purple skin rash that spreads and causes blistering and peeling).

Seek medical treatment if you have a serious drug reaction that can affect many parts of your body. Symptoms may include: skin rash, fever, swollen glands, muscle aches, severe weakness, unusual bruising, or yellowing of your skin or eyes.

Report any new or worsening symptoms to your doctor, such as: mood or behavior changes, anxiety, panic attacks, trouble sleeping, or if you feel impulsive, irritable, agitated, hostile, aggressive, restless, hyperactive (mentally or physically), more depressed, or have thoughts about suicide or hurting yourself.

Call your doctor at once if you have:

  • slow or uneven heartbeats, chest pain, fluttering in your chest, and dizziness (like you might pass out);
  • any skin rash, no matter how mild;
  • fever, chills, sore throat, swollen glands;
  • red or swollen gums, mouth sores;
  • easy bruising, unusual bleeding, purple or red spots under your skin; or
  • liver problems – loss of appetite, upper stomach pain, dark urine, clay-colored stools, jaundice (yellowing of the skin or eyes).

Common phenytoin side effects may include:

  • drowsiness, confusion;
  • slurred speech;
  • abnormal eye movement; or
  • problems with balance or muscle movement.

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* The Content is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition.