Tikosyn (dofetilide) is an antiarrhythmic drug that is used to treat an abnormal heartbeat. Antiarrhythmic drugs are classified using a system known as the Vaughan Williams Classification System and under this system Tikosyn is classed as a Class III antiarrhythmic, which is a group of drugs that act as potassium channel blockers.

Tikosyn works by blocking specific potassium channels called inward-rectifier potassium channels (IKr) in the heart. This increases the effective refractory period (ERP) - or resting period - that occurs after a heart muscle cell (cardiac myocyte) has responded to the electrical charge (action potential). Increasing the amount of time a cell rests for helps to prevent certain types of arrhythmias.

Tikosyn was first approved by the US Food and Drug Administration (FDA) on 1 October 1999. Generic versions of this medication are also available.

What is Tikosyn used for?

Tikosyn is a prescription medicine that is used to treat an irregular heartbeat (atrial fibrillation or atrial flutter).

It is not known if this medication is safe and effective in children under 18 years of age.

Tikosyn has also been used 'off-label' in patients with supraventricular arrhythmias, ventricular tachycardia, and Wolff-Parkinson-White syndrome.

Tikosyn can cause serious side effects, including a type of abnormal heartbeat called Torsade de Pointes, which can lead to death.

To establish the right dose of this medication, treatment with Tikosyn must be started in a hospital where your heart rate and kidney function will be checked for the first 3 days of treatment. It is important that when you go home, you take the exact dose of Tikosyn that your doctor prescribed for you.

While you take this medication, always watch for signs of abnormal heartbeat.

Call your doctor and go to the hospital right away if you:

• feel faint
• become dizzy, or
• have a fast heartbeat

• Take Tikosyn exactly as your doctor tells you.
• Do not change your dose unless your doctor tells you to.
• Your doctor will do tests before you start and while you take this medication.
• Do not stop taking this medication until your doctor tells you to stop.
• Tikosyn can be taken with or without food.

The usual recommended dose of Tikosyn is 500 mcg taken orally twice a day, but this dose may need to be modified using the dosing algorithm supplied in the full prescribing information.

The dose of this Tikosyn must be individualized according to calculated creatinine clearance and QTc (corrected for heat rate). QT interval should be used if the heart rate is <60 beats per minute. There are no data on use of this medication when the heart rate is <50 beats per minute.

See the full prescribing information for further details about Tikosyn dosing.

Do not take Tikosyn if you:

• have an irregular heartbeat called long QT syndrome
• have kidney problems or are on kidney dialysis
• take any of these medicines:
  • cimetidine (Tagamet, Tagamet HB)
  • verapamil (Calan, Calan SR, Covera-HS, Isoptin, Isoptin SR, Verelan, Verelan PM, Tarka)
  • ketoconazole (Nizoral, XolegelL, Extina)
  • trimethoprim alone (Proloprim, Trimpex) or the combination of trimethoprim and sulfamethoxazole (Bactrim, Septra Sulfatrim)
  • prochlorperazine (Compazine, Compo)
  • megestrol (Megace)
  • dolutegravir (Tivicay)
  • hydrochlorothiazide alone or in combination with other medicines (such as Esidrix, Ezide, Hydrodiuril, Hydro-par, Microzide, or Oretic)
    
    Ask your doctor if you are not sure if any of your medicines are the kind listed above.
• are allergic to dofetilide in Tikosyn. See below for a complete list of ingredients in this medication.

What should I tell my doctor before taking Tikosyn?

Before taking Tikosyn, tell your doctor about all of your medical conditions including if you:

• have heart problems
• have kidney or liver problems

Especially tell your doctor if you take medicines to treat:

• heart problems
• high blood pressure
• depression or other mental problems
• asthma
• allergies, or hay fever
• skin problems
• Infections

Ask your doctor if you are not sure about the medicines you take.

If you miss a dose of Tikosyn, just take the next dose at your regular time. Do not take 2 doses of this medication at the same time.

If you take too much Tikosyn, call your doctor or go to the nearest hospital emergency room right away. Take your capsules with you to show to the doctor.

Tikosyn can cause serious side effects, including a type of abnormal heartbeat called Torsade de Pointes, which can lead to death. See 'Important information' above.

The most common side effects of Tikosyn include:

• headache
• chest pain
• dizziness

Call your doctor right away if you have signs of electrolyte imbalance including:

• severe diarrhea
• unusual sweating
• vomiting
• not hungry (loss of appetite)
• increased thirst (drinking more than normal)

Tell your doctor if you have any side effects that bother you or do not go away.

These are not all the possible side effects of this medication. For more information, ask your doctor or pharmacist. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Tell your healthcare provider about all the medicine you take, including prescription and over-the-counter medicines, vitamins, and herbal supplements.

Tikosyn and other medicines may affect each other, causing serious side effects. If you take Tikosyn with certain medicines, you will be more likely to have a different type of abnormal heartbeat. See "Who should not take Tikosyn?" above for a list of medications.

Know the medicines you take. Keep a list of your medicines and show it to your doctor and pharmacist when you get a new medicine.