Dilantin (phenytoin) is a brand-name drug that’s prescribed for certain types of seizures in adults and children. Dilantin can cause side effects that range from mild to serious, such as drowsiness or confusion.

Dilantin injection has a boxed warning. A boxed warning is the most serious warning from the Food and Drug Administration (FDA). For details, see the “Side effect specifics” section below.

Dilantin can cause certain side effects, some of which are more common than others. These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

These are just a few of the more common side effects reported by people who took Dilantin in clinical trials of Dilantin capsules, Dilantin chewable tablets, or Dilantin injection:

* For more information about this side effect, see “Side effect specifics” below.

Mild side effects can occur with Dilantin use. This list doesn’t include all possible mild side effects of the drug. For more information, you can refer to the prescribing information for Dilantin capsules, Dilantin chewable tablets, or Dilantin injection.

Mild side effects that have been reported with Dilantin include:

These side effects may be temporary, lasting a few days to weeks. However, if the side effects last longer than that, bother you, or become severe, be sure to talk with your doctor or pharmacist.

Note: After the FDA approves a drug, it tracks and reviews side effects of the medication. If you develop a side effect while taking Dilantin and want to tell the FDA about it, visit MedWatch.

* For more information about this side effect, see “Side effect specifics” below.

Dilantin may cause serious side effects. The list below may not include all possible serious side effects of the drug. For more information, you can refer to the prescribing information for Dilantin capsules, Dilantin chewable tablets, or Dilantin injection.

If you develop serious side effects while taking Dilantin, call your doctor right away. If the side effects seem life threatening or you think you’re having a medical emergency, immediately call 911 or your local emergency number.

Serious side effects that have been reported and their symptoms include:

  • severe skin rashes, including Stevens-Johnson syndrome or toxic epidermal necrolysis, which may cause symptoms such as:
    • skin redness or discoloration
    • peeling or blistering of your skin
    • painful sores in your mouth
    • flu-like symptoms
  • DRESS syndrome (a type of severe allergy), which may cause symptoms such as:
    • skin rash
    • swollen lymph nodes
    • fever
  • suicidal thoughts or behaviors, which may cause symptoms such as:
    • changes in sleep
    • feelings of anxiety, sadness, and hopelessness
    • severe mood swings
    • thoughts of dying
  • liver problems, including liver failure, which may cause symptoms such as:
    • nausea and vomiting
    • dark-colored urine or pale stool
    • yellowing of your skin or the white parts of your eyes
    • fever
  • decreased blood cell counts, which may cause symptoms such as:
    • frequent infections or an infection that doesn’t go away
    • easy bruising or bleeding
    • tiredness
  • hyperglycemia (increased blood sugar), which may cause symptoms such as:
  • heart problems, which may cause symptoms such as:
    • a feeling like your heart is beating slowly
    • fainting
    • dizziness
    • chest pain
  • angioedema (swelling under your skin), which may cause symptoms such as:
    • sudden swelling of your face, lips, tongue, or throat
    • trouble swallowing, breathing, or talking
  • decreased bone mineral density, which may cause symptoms such as:
    • bone fractures
  • risk of cardiovascular problems with rapid infusion of phenytoin injection*

* For more information about this side effect, see “Side effect specifics” below.

ALLERGIC REACTION

For some people, Dilantin can cause an allergic reaction.

In general, symptoms of allergic reaction can be mild or serious. You can learn more about possible symptoms in this article.

Ways to manage

For mild allergic reaction symptoms, such as a mild rash, call your doctor right away. They may recommend treatments to help manage your symptoms. They’ll also let you know whether you should keep taking the medication.

For severe allergic reaction symptoms, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms require immediate medical care because they can become life threatening. If you’ve had a serious allergic reaction to Dilantin, your doctor may recommend taking a different medication instead.

Dilantin may cause several side effects. Here are some frequently asked questions about the drug’s side effects and their answers.

Does Dilantin cause long-term side effects?

Yes, Dilantin can cause long-term side effects. Long-term side effects include those that start at any time during therapy or those that don’t go away, even after stopping the drug. Some of the long-term side effects Dilantin can cause are:

  • peripheral neuropathy (nerve damage), which can lead to a tingling or numbing in your hands or feet
  • a decrease in the levels of vitamin D in your blood, which can lead to osteopenia or osteoporosis and may increase your risk of bone fractures
  • gingival hyperplasia, which is when your gums swell and may grow around or over your teeth
  • coarsening of facial features, such as an enlarged nose and thickened lips and skin
  • increased hair growth on your face or body
  • problems with your memory or your ability to think clearly

Talk with your doctor if you have questions or concerns about long-term side effects with Dilantin.

Is Dilantin safe for older adults?

Yes, it is safe for older adults to take Dilantin. As you age, it takes longer for your body to clear medication from your system. This can increase your risk for side effects. Because of this, your doctor may prescribe a lower dosage or a different treatment schedule for you.

Older adults may also be more sensitive to some of the side effects of Dilantin, such as osteoporosis or problems with thinking or memory.

If you have any concerns about side effects you may experience during treatment with Dilantin, talk with your doctor.

Can Dilantin cause a change in urine color?

It’s possible. While changes in urine color haven’t been reported in clinical studies of the drug, there are reports that Dilantin can cause urine to turn pink or brown.

In rare cases, Dilantin can cause liver damage. One symptom of liver problems is dark-colored urine. If you have dark-colored urine along with other symptoms such as stomach pain, fever, or nausea, talk with your doctor right away.

Learn more about some of the side effects that Dilantin may cause. To find out how often side effects occurred in clinical trials, see the prescribing information for Dilantin capsules, Dilantin chewable tablets, or Dilantin injection.

Risk of cardiovascular problems with rapid infusion of Dilantin

Dilantin injection has a boxed warning about the risk of cardiovascular problems with rapid infusion. Boxed warnings are the most serious warnings from the FDA.

Dilantin can be given by intravenous (IV) infusion (into a vein over time) in cases where it can’t be taken by mouth. If given too quickly, Dilantin can cause serious side effects, including an irregular heartbeat, a slow heart rate, or severe low blood pressure. Serious side effects are more likely to occur in people with certain serious conditions and in adults ages 65 years or older.

What you can do

Dilantin infusions are typically given in a hospital. Your doctor will closely monitor you for serious side effects during and after the infusion. If you have side effects during your infusion, your doctor may decrease your dose or give your infusion more slowly.

Problems with coordination

Ataxia (problems with coordination) is a common side effect reported in clinical studies with Dilantin. You might notice that you are unsteady on your feet, feel off-balance, or have difficulty with fine motor skills.

What you can do

You can reduce your chances of falling by taking safety precautions. Remove any tripping hazards in your home, such as throw rugs or shower mats with a slippery surface. You can also try exercises, such as yoga, to improve your coordination and balance.

You shouldn’t drive, use machinery, or do other tasks that require alertness until you know how this drug affects you.

Talk with your doctor if you’re experiencing new or worsening problems with coordination. Worsening symptoms may be caused by high blood levels of Dilantin. Your doctor will likely check your Dilantin blood levels and may need to adjust your dose.

Suicide prevention

If you know someone at immediate risk of self-harm, suicide, or hurting another person:

  • Ask the tough question: “Are you considering suicide?”
  • Listen to the person without judgment.
  • Call 911 or the local emergency number, or text TALK to 741741 to communicate with a trained crisis counselor.
  • Stay with the person until professional help arrives.
  • Try to remove any weapons, medications, or other potentially harmful objects if it’s safe to do so.

If you or someone you know is having thoughts of suicide, a prevention hotline can help. The 988 Suicide and Crisis Lifeline is available 24 hours a day at 988. During a crisis, people who are hard of hearing can use their preferred relay service or dial 711 then 988.

Find more links and local resources.

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Below is important information you should consider before taking Dilantin.

Dilantin injection has a boxed warning. A boxed warning is the most serious warning from the FDA. For details, see the “Side effect specifics” section above.

Other precautions

Before taking Dilantin, discuss your health history with your doctor. Dilantin may not be right for you if you have certain medical conditions or other factors affecting your health. Be sure to talk with your doctor if any of the following apply to you:

  • current or past depression, mood problems, or suicidal thoughts
  • kidney or liver problems
  • current or past porphyria (a blood disorder)
  • hyperglycemia (high blood sugar)
  • previous allergic reaction to Dilantin or a similar drug
  • pregnancy
  • breastfeeding
  • alcohol consumption

Disclaimer: Medical News Today has made every effort to make certain that all information is factually correct, comprehensive, and up to date. However, this article should not be used as a substitute for the knowledge and expertise of a licensed healthcare professional. You should always consult your doctor or another healthcare professional before taking any medication. The drug information contained herein is subject to change and is not intended to cover all possible uses, directions, precautions, warnings, drug interactions, allergic reactions, or adverse effects. The absence of warnings or other information for a given drug does not indicate that the drug or drug combination is safe, effective, or appropriate for all patients or all specific uses.