As with other drugs, Tecfidera (dimethyl fumarate) can cause side effects, such as rash, nausea, or vomiting. If you’re not able to tolerate side effects of Tecfidera, talk with your doctor or pharmacist.

Tecfidera (dimethyl fumarate) is a brand-name delayed-release capsule that’s prescribed for certain types of multiple sclerosis (MS).

If you have problems with side effects from Tecfidera, talk with your doctor or pharmacist. They can discuss ways to manage side effects or other available treatment options. Do not stop taking Tecfidera without consulting your doctor first.

For additional information about Tecfidera, including details about its uses, see this Tecfidera overview article.

Tecfidera 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 persist, 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 Tecfidera in clinical trials:

For more information about some of these side effects, see the “Side effect specifics” section.

Mild side effects can occur while taking Tecfidera. This list does not include all possible mild side effects of the drug. For more information, you can refer to Tecfidera’s prescribing information.

Mild side effects reported by people taking Tecfidera 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.

For more information about some of these side effects, see the “Side effect specifics” section.

Note: After the Food and Drug Administration (FDA) approves a drug, it tracks side effects of the medication. If you develop a side effect while taking Tecfidera and want to tell the FDA about it, visit MedWatch.

Tecfidera 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 Tecfidera’s prescribing information.

If you develop serious side effects while taking Tecfidera, 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:

  • Lymphocytopenia (low level of lymphocytes, a type of white blood cell). This condition does not directly cause symptoms. However, it can increase your risk of contracting an infection.
  • Serious infection.
  • Severe flushing.
  • Liver damage.

For more information about some of these side effects, see the “Side effect specifics” section.

Allergic reaction

For some people, Tecfidera can cause an allergic reaction. However, it’s not clear how often this side effect occurred in the drug’s studies.

In general, symptoms of allergic reaction can be mild or serious.

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 Tecfidera, your doctor may recommend taking a different medication instead.

Tecfidera is not known to cause long-term side effects.

However, Tecfidera may increase your risk of infections, and some infections may cause long-term problems. For example, a shingles infection may cause lasting nerve problems. Rarely, brain infections may occur while taking Tecfidera, and some serious brain infections can lead to severe, permanent disabilities. These infections have occurred in people who have taken Tecfidera for a long time.

Tecfidera’s common side effects, such as flushing and nausea, are usually temporary. These side effects are more common when you first start the drug. These side effects usually go away within a month.

If side effects from Tecfidera become severe or do not go away, talk with your doctor. They may suggest stopping treatment with the medication.

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

Flushing

Flushing is a common side effect of Tecfidera. In fact, it was the most common side effect seen in people taking this medication in clinical trials.

Flushing occurs when the blood vessels just under your skin dilate (widen). Symptoms most commonly appear on your cheeks, neck, and chest. And these symptoms may include skin discoloration, warmth, or a burning sensation.

Flushing from Tecfidera is usually temporary or easily managed. Less commonly, flushing can be severe.

What you can do

Symptoms of flushing tend to be worse when you first start taking the drug. Flushing usually gets better or goes away after the first month of treatment.

It’s best to take Tecfidera with food to help prevent or ease this side effect.

Taking a non-coated aspirin tablet 30 minutes before taking Tecfidera may also help reduce or prevent flushing. The drug’s manufacturer suggests that aspirin doses of up to 325 milligrams (mg) are effective. However, you should talk with your doctor about how much aspirin (if any) is safe for you.

Digestive problems

It’s common to have digestive problems while taking Tecfidera. These side effects are especially common at the start of treatment. Symptoms often include:

In Tecfidera’s clinical trials, digestive problems most often occurred within the first month of treatment. In some cases, these symptoms were severe enough that some people had to stop treatment.

What you can do

For most people, digestive problems with Tecfidera are temporary. The symptoms should become less bothersome or go away with continued use of the drug.

To help prevent or ease digestive problems from Tecfidera, it’s best to take each dose with food. Consider these other tips to help minimize or prevent digestive side effects:

  • Snack frequently: Some people feel more nauseous when their stomach is empty. It may help to keep crackers or dry cereal on hand to snack on.
  • Stay hydrated: When you experience vomiting and diarrhea, you may lose too much fluid. Make sure to drink water or electrolyte replacement beverages to help prevent dehydration.
  • Try to avoid foods that may aggravate an upset stomach: Eating fried or spicy foods could worsen digestive problems such as indigestion or diarrhea. Consider choosing non-fried or bland foods for a while after starting treatment with this medication.

It’s important to talk with your doctor if your symptoms do not go away or become severe. Your doctor may temporarily reduce your dose of Tecfidera to see if the side effects ease.

Less commonly, digestive problems could be a sign of liver damage, a potentially serious side effect of Tecfidera. If this is the case, your doctor may have you temporarily or permanently stop the medication.

Serious infection

People taking Tecfidera may have an increased risk of serious viral, bacterial, or fungal infections. This includes serious infections of the eyes, ears, brain, meninges (tissues surrounding the brain), spinal cord, digestive tract, and lungs.

Serious infections were rare in Tecfidera’s clinical trials. However, since the drug was approved for use in 2013, there have been reports of serious infections in people taking it. It isn’t clear how often this has occurred or if Tecfidera was the cause.

If you’ve had exposure to the varicella-zoster virus, which causes chickenpox, Tecfidera can cause this virus to reactivate (flare up and cause symptoms). This can lead to a serious shingles infection (also known as herpes zoster), which can affect the eyes or brain.

Some people have developed a serious brain infection called progressive multifocal leukoencephalopathy (PML) while taking Tecfidera, but this is rare. Caused by the John Cunningham (JC) virus, PML may lead to severe disability and, in some cases, death. Symptoms may include:

  • weakness on one side of the body
  • clumsiness
  • vision changes
  • confusion
  • changes in your personality

During clinical trials of Tecfidera, one person died from PML after taking the drug for 4 years. During the trial, this person experienced prolonged lymphopenia (low levels of lymphocytes, a type of white blood cell.

What you can do

Your doctor will order blood tests to monitor your white blood cell levels before you start taking Tecfidera and regularly during treatment. If you have lymphopenia, your risk of developing infections is higher. Because of this risk, your doctor may not have you start or continue taking the drug.

If you develop symptoms of a possible infection, tell your doctor right away. If they suspect or confirm that you have an infection, they’ll likely treat it. Your doctor will also likely have you stop taking Tecfidera until the infection has cleared up.

Liver damage

In Tecfidera’s clinical trials, some people had certain changes seen on liver function tests. These changes included increased liver enzymes and high bilirubin levels.

These changes can sometimes be an early sign of liver damage. However, in these trials, no one had liver damage.

There have been reports of serious liver problems in people taking Tecfidera. However, it’s unclear how often this has happened or if Tecfidera was the cause.

Symptoms of liver damage can include:

What you can do

Before you start taking Tecfidera, your doctor will check the health of your liver using blood tests. These tests will help your doctor decide if your liver is working well enough for you to take the drug. During your treatment, your doctor will recheck these tests regularly.

If you develop signs or symptoms of liver damage, your doctor will likely have you stop taking Tecfidera.

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

Are weight gain or fatigue side effects of Tecfidera?

Tecfidera should not cause weight gain or fatigue. These side effects were not seen in the drug’s clinical trials.

However, fatigue is a symptom of multiple sclerosis (MS). Doctors prescribe Tecfidera to treat MS. And weight gain is common among people with MS. This is because some MS symptoms can reduce a person’s ability to exercise. These symptoms include low energy levels, stiffness, and balance problems.

Fatigue can also be a symptom of liver damage, a rare, potentially serious side effect Tecfidera may cause.

Talk with your doctor if you have weight gain or fatigue while taking Tecfidera. They can suggest ways to manage these symptoms.

Does Tecfidera cause hair loss?

No, hair loss was not a side effect reported by people who took Tecfidera in clinical trials.

In one report, a person had temporary hair loss during the first few months of taking Tecfidera for relapsing-remitting multiple sclerosis (RRMS). Their hair loss improved over a few more months of continued treatment. And it is not known for sure if the drug was the cause.

If you notice hair loss while taking Tecfidera, talk with your doctor. They may be able to help find what’s causing your hair loss and suggest ways to manage it.

Should I expect any side effects when stopping Tecfidera treatment?

No, stopping Tecfidera treatment shouldn’t cause side effects. However, stopping this medication may lead to worsened symptoms or progression of MS.

If you have questions about stopping treatment with Tecfidera, talk with your doctor. They can guide you on whether a different treatment option would be better for you.

Do Tecfidera’s side effects vary between the 120-mg and 240-mg strengths?

No, Tecfidera’s possible side effects are the same with both strengths. However, it’s important to note that only the maintenance (ongoing) dosage of Tecfidera has been shown to be effective for the drug’s approved uses. The recommended maintenance dosage is 240 milligrams (mg) twice per day. Typically, you will only take the lower strength (120 mg) as a starting dose twice daily for the first week of treatment.

Some people have digestive problems, such as nausea and diarrhea, when they start taking the maintenance dosage. In this situation, your doctor may suggest temporarily reducing your dose of Tecfidera to 120 mg twice per day. However, your doctor will likely only prescribe this lower strength short term for up to 4 weeks because it may not treat your condition effectively. If digestive problems remain severe at this dose, your doctor will likely recommend switching to a different treatment option.

If you have additional questions about the side effects of different Tecfidera strengths, talk with your doctor.

Are teeth-related side effects possible with Tecfidera?

Tecfidera should not cause tooth problems. People who took the drug in clinical trials did not report any teeth-related side effects.

People with MS may have more dental problems than those without the condition. It’s thought that certain MS symptoms could make oral health practices more challenging. For example, some people with MS have numbness or tremors in their hands. This can make it harder to grip or maneuver a toothbrush and floss.

If you have a toothache or other tooth-related problems, talk with your dentist. They can recommend ways to fix the problem and maintain good oral hygiene.

Before taking Tecfidera, discuss your health history with your doctor. Tecfidera 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:

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.