Tikosyn (dofetilide) is a prescription oral capsule used to treat certain heart arrhythmias. Tikosyn can cause side effects that range from mild to serious. Examples include headache and chest pain.

Tikosyn is used in adults to:

The active ingredient in Tikosyn is dofetilide. (An active ingredient is what makes a drug work.) The drug comes as a capsule you swallow.

Keep reading to learn about the common, mild, and serious side effects Tikosyn can cause. For a general overview of the drug, including details about its uses, see this article.

Some people may experience mild to serious side effects during their Tikosyn treatment. Examples of the drug’s commonly reported side effects include:

Mild side effects have been reported with Tikosyn. These include:

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 do not stop taking Tikosyn unless your doctor recommends it.

Tikosyn may cause mild side effects other than those listed above. See the drug’s prescribing information for details.

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

Serious side effects have been reported with Tikosyn. These include:

If you develop serious side effects while taking Tikosyn, 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.

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 a side effect you’ve had with Tikosyn, visit MedWatch.

Get answers to some frequently asked questions about Tikosyn’s side effects.

Can Tikosyn cause weight gain?

No, it’s not expected to. Weight gain wasn’t reported as a side effect in Tikosyn’s studies.

Rarely, Tikosyn can cause edema (swelling and fluid retention, such as in your arms or legs). If severe, edema could cause temporary weight gain until it’s successfully treated. But Tikosyn isn’t expected to cause long-term weight gain.

Talk with your doctor if you have questions or concerns about your weight while taking Tikosyn.

Will I experience side effects when stopping Tikosyn?

No, withdrawal symptoms weren’t reported in Tikosyn’s studies, and this drug isn’t known to cause dependence. (Withdrawal symptoms are side effects that can happen when you stop taking a drug your body has become dependent on. Dependence is when your body gets used to a drug and needs it for you to function as usual.)

Still, you should not stop taking Tikosyn unless your doctor agrees it’s safe for you to do so. This drug is used to treat an irregular heart rhythm, and it’s important that your doctor checks your heart health before you stop taking the drug to be sure it’s safe.

If you have questions about stopping Tikosyn, talk with your doctor.

Does Tikosyn cause long-term side effects?

Yes. It’s rare but possible for Tikosyn to cause long-term side effects. Examples reported in the drug’s studies include:

  • angina (a type of chest pain), which may or may not go away after stopping Tikosyn treatment
  • cardiac arrest, which is a life threatening medical emergency that can cause long-term effects
  • heart attack,* a life-threatening medical emergency that can cause long-term effects
  • liver damage, which may not go away even after stopping Tikosyn treatment
  • paralysis, including in your face*
  • boxed warning: risk of new or worsening arrhythmia*

Talk with your doctor or pharmacist if you have additional questions about Tikosyn and long-term side effects.

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

Learn more about some of the side effects Tikosyn may cause.

Risk of new or worsening arrhythmia

Tikosyn has a boxed warning for the risk of a new or worsening arrhythmia (irregular heart rhythm). A boxed warning is the most serious warning from the Food and Drug Administration (FDA).

Treatment with Tikosyn can cause a new heart arrhythmia, including torsades de pointes, which can be life threatening. This drug can also worsen an existing arrhythmia. (Tikosyn is prescribed to maintain a healthy heart rhythm in people with atrial fibrillation (AFib) and to convert AFib or atrial flutter into a healthy heart rhythm.)

In some cases, a heart arrhythmia doesn’t cause symptoms. But in other cases, you may experience symptoms including:

Your risk for this side effect is higher if you have a kidney condition, such as chronic kidney disease. It may also be higher if you have an existing heart condition or problem, such as heart disease.

Due to the risk of a new or worsening arrhythmia, your doctor likely will not prescribe Tikosyn if you:

They may also avoid prescribing Tikosyn if you take certain other drugs that interact with Tikosyn. They can recommend other treatments for your condition that may be safer for you.

What might help

You must start treatment with Tikosyn in a hospital or clinic. This is so your heart rhythm and kidney function can be monitored for at least 3 days. In the event of a heart arrhythmia during this time, healthcare professionals will be on hand to quickly treat your symptoms.

Changes in electrolyte levels, including potassium and magnesium, can also affect your risk of heart arrhythmias. Before and during your treatment, your doctor will order tests to check the level of potassium in your blood. They can provide more information on how frequently they’ll need to check your electrolyte levels.

During treatment with Tikosyn, your doctor will monitor your heart health and rhythm, as well as your kidney function. If they notice signs of a heart rhythm or kidney function problem, they may adjust your Tikosyn dose or recommended you stop taking the drug.

Paralysis, including in your face

Paralysis is a rare but potential side effect reported in the drug’s studies. Paralysis caused by Tikosyn can affect any part of your body, including your face. It can be difficult to distinguish between facial paralysis and a stroke, another rare side effect this drug can cause. Symptoms of paralysis include:

  • loss of function in specific or widespread areas of your body
  • inability to control affected muscles
  • progressive weakness in any part of your body

What might help

Immediately contact your doctor if you experience symptoms of paralysis while taking Tikosyn. If you think you’re having a stroke, immediately call 911 or go to the nearest emergency room.

Paralysis caused by Tikosyn may go away with treatment and once you stop taking Tikosyn. An example of a treatment your doctor may prescribe is a corticosteroid drug such as Medrol (methylprednisolone).

Heart attack

Heart attack was reported as a rare side effect in Tikosyn’s studies. Symptoms of a heart attack can include:

  • severe chest pain that may radiate to your neck, back, shoulder, or arm
  • feeling nauseous, lightheaded, or dizzy
  • shortness of breath
  • sweating

What might help

Immediately call 911 or seek emergency medical services (such as the nearest emergency room) if you think you’re having symptoms of a heart attack. This is a life threatening emergency that requires immediate treatment in a hospital or emergency department.

If you experience a heart attack while taking Tikosyn, your doctor may recommend switching you to a different treatment for your condition.

Allergic reaction

Like most drugs, Tikosyn can cause an allergic reaction in some people. These reactions were rare in Tikosyn’s studies. 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 (usually 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 a treatment to manage your symptoms. Examples include:

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

Keeping track of side effects

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

Your side effect notes can include things such as:

  • what dose of the drug you were taking when you had the side effect
  • how soon you had the side effect after starting that dose
  • what your symptoms were
  • how your symptoms affected your daily activities
  • what 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 Tikosyn affects you. They can then use this information to adjust your treatment plan if needed.

There are important warnings to consider before starting treatment with Tikosyn.

Boxed warning: Risk of a new or worsening arrhythmia

Tikosyn has a boxed warning for the risk of a new or worsening arrhythmia. A boxed warning is the most serious warning from the Food and Drug Administration (FDA).

Tikosyn treatment can cause a new arrhythmia or worsen an existing one. (Tikosyn is prescribed to treat and manage certain heart arrhythmias.)

To learn more, see the “Side effects explained” section above.

Other warnings

Tikosyn may not be right for you if you have certain medical conditions. This is known as a drug-condition interaction. Other factors may also affect whether this drug is a good treatment option for you. Talk with your doctor about your health history before starting Tikosyn. Factors to consider include those described below.

Kidney condition. Your doctor will calculate your Tikosyn dose based on your kidney function. It’s not known whether it’s safe for people with severe kidney problems, such as end-stage kidney disease, to take this drug. Be sure to talk with your doctor about any kidney conditions you may have before starting Tikosyn. They can determine if the medication is safe for you to take.

Liver condition. In rare cases, Tikosyn can cause liver damage as a side effect. If you have an existing liver condition, such as cirrhosis, this drug could worsen your condition. Talk with your doctor about whether Tikosyn is safe for you to take with your liver condition.

Allergic reaction. If you’ve had an allergic reaction to Tikosyn or any of its ingredients, your doctor will likely not prescribe it for you. Ask them about other medications that might be better options.

Alcohol and Tikosyn

There are no known interactions between Tikosyn and alcohol. Talk with your doctor if you have questions about consuming alcohol during treatment with this drug.

Pregnancy and breastfeeding with Tikosyn

It’s not known whether it’s safe to take Tikosyn while pregnant. It’s also not known if it’s safe to breastfeed a child while taking this drug, but the manufacturer recommends against it.

Talk with your doctor to learn more about the risks and benefits of treatment options for your condition if you’re pregnant, breastfeeding, or plan to be either.

Like most drugs, Tikosyn carries a risk of side effects. Most side effects of the drug are mild and go away on their own, but serious side effects have occurred in rare cases. If you have questions about side effects Tikosyn can cause, talk with your doctor. Examples to help get you started include:

  • Is it safe for me to take Tikosyn based on my health history?
  • Do any of the other drugs I take interact with Tikosyn or increase my risk of side effects?
  • If I have side effects from Tikosyn, can you prescribe a lower dosage for me?

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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.