Pacerone affects the rhythm of your heartbeats.

Pacerone is used to help keep the heart beating normally in people with life-threatening heart rhythm disorders of the ventricles (the lower chambers of the heart that allow blood to flow out of the heart). This medicine is used to treat ventricular tachycardia or ventricular fibrillation.

Pacerone is for use only in treating life-threatening heart rhythm disorders.

Pacerone may also be used for purposes not listed in this medication guide.

Pacerone is for use only in treating life-threatening heart rhythm disorders.

You should not take Pacerone if you are allergic to Pacerone or iodine, or if you have heart block, a history of slow heartbeats that have caused you to faint, or if your heart cannot pump blood properly.

Pacerone can cause dangerous side effects on your heart, liver, lungs, or vision.

Call your doctor or get medical help at once if you have: chest pain, fast or pounding heartbeats, trouble breathing, vision problems, upper stomach pain, vomiting, dark urine, jaundice (yellowing of the skin or eyes), or if you cough up blood.

Follow all directions on your prescription label and read all medication guides or instruction sheets. Your doctor may occasionally change your dose. Use the medicine exactly as directed.

You will receive your first few doses in a hospital setting, where your heart rhythm can be monitored.

If you have been taking another heart rhythm medicine, you may need to gradually stop taking it when you start using Pacerone. Follow your doctor's dosing instructions very carefully.

You may take Pacerone with or without food, but take it the same way each time.

It may take up to 3 weeks before your heart rhythm improves. Keep using the medicine as directed even if you feel well.

Pacerone can have long lasting effects on your body. You may need frequent medical tests while using Pacerone and for several months after your last dose.

If you need surgery (including laser eye surgery), tell the surgeon ahead of time that you are using Pacerone.

This medicine can affect the results of certain medical tests. Tell any doctor who treats you that you are using Pacerone.

Store at room temperature away from moisture, heat, and light.

You should not use this medicine if you are allergic to Pacerone or iodine, or if you have:

• a serious heart condition called "AV block" (2nd or 3rd degree), unless you have a pacemaker;

• a history of slow heartbeats that have caused you to faint; or

• if your heart cannot pump blood properly.

Pacerone can cause dangerous side effects on your heart, liver, lungs, or thyroid.

Tell your doctor if you have ever had:

• asthma or another lung disorder;

• liver disease;

• a thyroid disorder;

• vision problems;

• high or low blood pressure;

• an electrolyte imbalance (such as low levels of potassium or magnesium in your blood); or

• if you have a pacemaker or defibrillator implanted in your chest.

Taking Pacerone during pregnancy may harm an unborn baby, or cause thyroid problems or abnormal heartbeats in the baby after it is born. This medicine may also affect the child's growth or development (speech, movement, academic skills) later in life. Tell your doctor if you are pregnant or if you become pregnant.

You should not breast-feed while taking Pacerone, and for several months after stopping. This medicine takes a long time to clear from your body. Talk to your doctor about the best way to feed your baby during this time.

Skip the missed dose and use your next dose at the regular time. Do not use two doses at one time.

Seek emergency medical attention or call the Poison Help line at 1-800-222-1222. An overdose of Pacerone can be fatal.

Overdose symptoms may include weakness, slow heart rate, feeling light-headed, or loss of consciousness.

Avoid driving or hazardous activity until you know how Pacerone will affect you. Your reactions could be impaired.

Grapefruit may interact with Pacerone and lead to unwanted side effects. Avoid the use of grapefruit products.

Avoid taking an herbal supplement containing St. John's wort.

Pacerone could make you sunburn more easily. Avoid sunlight or tanning beds. Wear protective clothing and use sunscreen (SPF 30 or higher) when you are outdoors.

Get emergency medical help if you have signs of an allergic reaction: hives; difficulty breathing; swelling of your face, lips, tongue, or throat.

Pacerone takes a long time to completely clear from your body. You may continue to have side effects from this medicine after you stop using it.

Call your doctor at once if you have any of these side effects, even if they occur up to several months after you stop using Pacerone:

• wheezing, cough, chest pain, cough with bloody mucus, fever;

• a new or a worsening irregular heartbeat pattern (fast, slow, or pounding heartbeats);

• a light-headed feeling, like you might pass out;

• blurred vision, seeing halos around lights (your eyes may be more sensitive to light);

• liver problems--nausea, vomiting, stomach pain (upper right side), tiredness, dark urine, jaundice (yellowing of the skin or eyes);

• nerve problems--loss of coordination, muscle weakness, uncontrolled muscle movement, or a prickly feeling in your hands or lower legs;

• signs of overactive thyroid--weight loss, thinning hair, feeling hot, increased sweating, tremors, feeling nervous or irritable, irregular menstrual periods, swelling in your neck (goiter); or

• signs of underactive thyroid--weight gain, tiredness, depression, trouble concentrating, feeling cold.

Common side effects of Pacerone may include:

• nausea, vomiting, loss of appetite; or

• constipation.

This is not a complete list of side effects and others may occur. Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.

Sometimes it is not safe to use certain medications at the same time. Some drugs can affect your blood levels of other drugs you take, which may increase side effects or make the medications less effective.

Pacerone takes a long time to completely clear from your body. Drug interactions are possible for up to several months after you stop using this medicine. Talk to your doctor before taking any medication during this time. Keep track of how long it has been since your last dose of amiodarone.

Many drugs can affect Pacerone. This includes prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed here. Tell your doctor about all your current medicines and any medicine you start or stop using.