If you have multiple sclerosis (MS), your doctor might suggest Gilenya as a treatment option for you. It’s a prescription medication used to treat the following types of MS in people ages 10 years and older:

Gilenya may also be prescribed to treat clinically isolated syndrome (CIS). People with CIS often (but not always) develop MS later on.

If you and your doctor agree that Gilenya is working well for you, you’ll likely take it long term.

Gilenya comes as a capsule that you swallow. The active drug in Gilenya is fingolimod. (This is the ingredient that makes the medication work). Fingolimod is also the name of the generic version of Gilenya.

For more information about Gilenya, including details about its uses, see this in-depth article.

Like other drugs, Gilenya can cause mild or serious side effects. Keep reading to learn more.

Some people may experience mild to serious side effects during their Gilenya treatment. Examples of commonly reported side effects include:

* Rarely, abnormal liver tests can be a sign of liver damage, a serious side effect that Gilenya may cause. To learn more, see “Side effects explained” below.

These aren’t all the side effects reported in Gilenya’s studies. And not everyone will have side effects from this medication.

Like most medications, Gilenya may cause mild side effects. Examples that have been reported include:

* To learn more about this side effect, see the “Side effects explained” section below.
** Rarely, abnormal liver tests can be a sign of liver damage, a serious side effect that Gilenya may cause. To learn more, see “Side effects explained” below.

In most cases, these side effects should be temporary. And some may be easily managed. But if you have symptoms that are ongoing or bother you, talk with your doctor or pharmacist. And don’t stop taking Gilenya unless your doctor recommends it.

Gilenya may cause mild side effects other than the ones listed above. See Gilenya’s prescribing information for details.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you’d like to notify the FDA about any side effects you’ve had with Gilenya, visit MedWatch.

Rarely, taking Gilenya may cause serious side effects. Those that have been reported include:

If you develop serious side effects while taking Gilenya, 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.

* To learn more about this side effect, see the “Side effects explained” section below.

Gilenya is used to treat certain types of multiple sclerosis in children ages 10 years and older.

For the most part, side effects in studies were very similar for children and adults. But children were more likely to report seizures as a side effect, compared with adults.

A seizure can be a sign of a rare but serious side effect* of Gilenya. Symptoms of a seizure can include:

It’s important to call your child’s doctor right away if they have a seizure while taking Gilenya.

* A seizure can be a symptom of posterior reversible encephalopathy syndrome (PRES), a rare but serious side effect of Gilenya. See “side effects explained” below to learn more about PRES.

Learn more about some of the side effects that Gilenya may cause.

Ocular (eye-related) side effects

Treatment with Gilenya may cause eye-related side effects. But these were rare in the drug’s studies.

Taking Gilenya increases the risk of macular edema. (This involves fluid building up in a part of your eye called the retina.) This side effect is most likely during your first 3 to 4 months of treatment.

Symptoms of macular edema can include:

People at higher risk of this side effect while taking Gilenya are those with:

What might help

Your doctor will likely have you get an eye exam before you start taking Gilenya. You’ll then need to redo this exam 3 to 4 months after you’ve started the treatment.

If you have eye-related side effects, such as blurry vision, you’ll get further exams as needed. And if you do have eye-related symptoms, such as those above, tell your doctor right away.

Macular edema often improves after people stop taking Gilenya. But in extreme cases, some visual problems may not go away, even with treatment for macular edema.

Skin cancer

People taking Gilenya in studies had a higher risk of skin cancer, compared with people taking a placebo. (A placebo is a treatment with no active drug.) But it’s important to note that skin cancer as a side effect of Gilenya is very rare.

Symptoms of skin cancer can include:

  • changes to a skin mole
  • a new darkened or discolored area of your skin
  • skin growths
  • sores that don’t heal
  • other changes to how your skin looks

What might help

Your doctor will monitor you for any symptoms of skin cancer while you’re taking Gilenya. And tell them right away if you notice any skin cancer symptoms.

Here are some tips to help reduce your risk of skin cancer:

  • limit your exposure to sunlight and UV light
  • use high SPF sunscreen
  • wear protective clothing, such as long sleeves or a hat, if you’ll be in the sun

Hair loss

Hair loss is a possible side effect of Gilenya, but it was rare in studies. And there weren’t reports of serious hair loss.

What might help

Tell your doctor if you have hair loss that bothers you while you’re taking Gilenya. They may recommend a treatment for this side effect. But they may also suggest that you stop taking Gilenya and try another multiple sclerosis (MS) treatment.

Posterior reversible encephalopathy syndrome (PRES)

PRES causes blood vessels in your brain to narrow and swell. This was very rare in studies of Gilenya, and it was only reported in adults taking the drug.

Symptoms of PRES appear very quickly over a few hours and can include:

PRES can be treated, but if a person does not receive treatment, it can lead to a stroke.

What might help

Call your doctor immediately if you notice symptoms of PRES while taking Gilenya. If they confirm that you have it, they’ll treat it and any symptoms you’re having. They’ll also have you stop taking Gilenya.

Liver damage

While it didn’t develop in studies, taking Gilenya can cause liver damage. This side effect has been reported since the drug was approved. In extreme cases, a few people needed a liver transplant.

Symptoms of liver damage can occur as early as 10 days after starting Gilenya treatment. But it can also occur after taking the drug for a long time. These symptoms can include:

Your risk of liver damage from Gilenya is higher if you already have severe liver problems.

What might help

Your doctor will order blood tests to check your liver function before prescribing Gilenya to you. They’ll continue ordering these tests while you take Gilenya and for at least 2 months after you stop the treatment.

Tell your doctor if you notice symptoms of liver damage while taking Gilenya. They’ll likely want to examine you in person and order lab tests to check your liver health.

If you have abnormal liver tests or symptoms of liver damage, your doctor may recommend that you stop taking Gilenya. They’ll likely suggest other MS treatment options for you.

Allergic reaction

Like most drugs, Gilenya can cause an allergic reaction in some people.

Symptoms can be mild to serious and can include:

  • skin rash
  • itchiness
  • flushing (temporary warmth, redness, or deepening of skin color)
  • swelling under your skin, typically in your eyelids, lips, hands, or feet
  • swelling of your mouth, tongue, or throat, which can make it hard to breathe

What might help

If you have mild symptoms of an allergic reaction, such as a mild rash, call your doctor right away. They may suggest an over-the-counter oral antihistamine, such as Benadryl (diphenhydramine), or a topical product, such as hydrocortisone cream, to manage your symptoms.

If your doctor confirms that you’ve had a mild allergic reaction to Gilenya, they’ll decide if you should continue taking it.

If you have symptoms of a severe allergic reaction, such as swelling or trouble breathing, call 911 or your local emergency number right away. These symptoms could be life threatening and require immediate medical care.

If your doctor confirms that you’ve had a serious allergic reaction to Gilenya, they may have you switch to a different treatment.

Keeping track of side effects

During your Gilenya treatment, consider keeping notes about any side effects you’re having. You can then share this information with your doctor. This is especially helpful when you first start taking new drugs or using a combination of treatments.

Your side effect notes can include things such as:

  • what dosage of drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dosage
  • what your symptoms were
  • how they affected your daily activities
  • any other medications you were taking
  • any other information you feel is important

Taking notes and sharing them with your doctor will help them learn more about how Gilenya affects you. They can then use this information to adjust your treatment plan if needed.

Below are answers to some frequently asked questions about Gilenya’s side effects.

Will stopping Gilenya treatment lead to withdrawal symptoms?

No, stopping the treatment doesn’t lead to withdrawal symptoms. But it may cause your multiple sclerosis (MS) symptoms to return.

And in some people, stopping this medication can lead to severe worsening of their MS. This is most likely to occur within 12 weeks of stopping the treatment, but it can also happen later. Often, this worsening isn’t reversible.

Do not stop taking Gilenya without first speaking with your doctor. And if you do stop taking it, contact your doctor right away if your MS symptoms start getting worse. Your doctor can suggest ways to treat them.

Is weight gain or weight loss a possible side effect of Gilenya?

No, neither weight gain nor weight loss were reported side effects in Gilenya’s studies.

Weight changes aren’t uncommon in people with MS. And some medications used to treat MS may cause weight changes. For example, steroids, such as prednisone (Rayos), used to treat MS flares can cause weight gain.

Talk with your doctor if you’re concerned about your weight. They can suggest ways for you to maintain a healthy weight.

Can Gilenya cause long-term side effects?

Though it’s not common, Gilenya can cause long-term side effects. They may start during the treatment or after it has ended.

These side effects may include:

  • worsening MS symptoms after stopping Gilenya treatment
  • progressive multifocal leukoencephalopathy, a rare but serious brain infection
  • eye-related side effects, such as:
    • vision loss
  • serious infection, including:

If you’re worried or have questions about long-term side effects of Gilenya, talk with your doctor or pharmacist.

Gilenya may not be right for you if you have certain medical conditions or other factors that affect your health. Talk with your doctor about your health history before starting Gilenya treatment. The list below includes factors to consider.

Breathing problems. Taking Gilenya can cause breathing problems, such as shortness of breath. If you already have breathing problems, such as from chronic obstructive pulmonary disease (COPD), your risk of this side effect may be higher. Your doctor can determine whether taking Gilenya is safe for you.

Eye problems. Gilenya may cause an eye-related side effect called macular edema. If you already have eye problems or diabetes, you may have a higher risk of this side effect. Your doctor can determine whether taking Gilenya is safe for you. They may choose to monitor your eye health more closely if they prescribe this medication for you.

Heart problems. Treatment with Gilenya can cause heart rhythm problems. If you already have an abnormal heart rhythm, your risk of this side effect may be higher. It may also increase your blood pressure as a side effect. If you have a history of heart problems, such as a heart attack, you may have a higher risk of these side effects. Due to the risk of heart problems, doctors typically won’t prescribe Gilenya if you’ve had a heart attack in the past 6 months or you have severe heart failure. Your doctor can determine whether taking this medication is safe for you. If they do prescribe Gilenya, they’ll probably have you stay in the hospital overnight after your first dose. This is so they can monitor your heart health.

History of stroke. If you’ve had a stroke or mini-stroke in the past 6 months, doctors typically will not prescribe Gilenya for you. This is because the drug may increase your risk of stroke, although this hasn’t been confirmed in studies.

Weakened immune system. Taking Gilenya increases your risk of infection. In rare cases, this can include serious infections, such as pneumonia or shingles. People who are immunocompromised (have a weakened immune system) may have a higher risk of infection while taking this drug. Your doctor can determine whether taking Gilenya is safe for you.

Liver problems. Taking Gilenya can cause liver problems. If you already have liver problems (such as hepatitis), your risk of this side effect may be higher. Your doctor can determine whether taking Gilenya is safe for you. They may choose to monitor your liver health more closely if they do prescribe it.

Skin cancer. Taking Gilenya increases your risk of skin cancer. Be sure to tell your doctor if you have or have had skin cancer. Gilenya may worsen your condition or cause the cancer to return.

Allergic reaction. If you’ve had an allergic reaction to Gilenya or any of its ingredients, your doctor will likely not prescribe it for you. Ask your doctor what other treatments might be better options.

Alcohol use and Gilenya

Alcohol isn’t known to interact with Gilenya. But drinking alcohol may increase your risk of certain side effects from this medication, including liver damage.

If you consume alcohol, talk with your doctor about whether there is a safe amount for you to drink while taking Gilenya.

Pregnancy and breastfeeding while taking Gilenya

Gilenya may cause harm if a person takes it during pregnancy. Due to this risk, doctors typically won’t prescribe this medication if you’re pregnant.

If you can become pregnant, they’ll recommend using effective birth control while taking the drug and for at least 2 months after stopping the treatment.

It’s not known if it’s safe to breastfeed while taking Gilenya. If you’re taking this medication, talk with your doctor about the best way to feed your child.

Like most medications, Gilenya can cause side effects. Many people take Gilenya without having side effects. And when these effects do occur, they’re usually mild for most people. In rare cases, Gilenya can cause severe side effects.

If you’re considering treatment with Gilenya, talk with your doctor. Ask questions that help you feel more comfortable about your treatment options. Some examples to get you started include:

  • If I have side effects while taking this medication, will taking a lower dosage help?
  • How do Gilenya’s side effects compare with those of other medications for multiple sclerosis (MS)?
  • If I have side effects while taking Gilenya, how long are they likely to last?

For tips on managing MS, details about treatments, and more, sign up for Healthline’s online newsletter.

Q:

Is it safe for me to get vaccines while taking Gilenya?

Anonymous

A:

It depends on the vaccine. You can safely get inactivated vaccines, such as:

But while taking Gilenya, you should not receive live vaccines. A few live vaccines include those for:

You should also not receive any live vaccines for 2 months after you stop taking Gilenya.

Before receiving any vaccine, be sure to talk with your doctor.

Dena Westphalen, PharmDAnswers represent the opinions of our medical experts. All content is strictly informational and should not be considered medical advice.

Disclaimer: Healthline 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.