Isochron is a nitrate that dilates (widens) blood vessels, making it easier for blood to flow through them and easier for the heart to pump.

Isochron is used to treat or prevent attacks of chest pain (angina).

Only the sublingual tablet should be used to treat an angina attack that has already begun.

Isochron regular and extended-release tablets are used to prevent angina attacks but will not treat an angina attack.

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

You should not take erectile dysfunction medicine (Viagra, Cialis, Levitra, Stendra, Staxyn, sildenafil, avanafil, tadalafil, vardenafil) while you are taking Isochron. Taking these medicine together can cause a sudden and serious decrease in blood pressure.

Seek emergency medical attention if you have early symptoms of a heart attack (chest pain or pressure, pain spreading to your jaw or shoulder, sweating, general ill feeling).

Before using Isochron to treat a sudden angina attack, your doctor may want you to first use a nitroglycerin sublingual tablet. Follow your doctor's instructions about what medications to use during an attack and how much time to allow between doses.

Follow all directions on your prescription label. Your doctor may occasionally change your dose. Do not take this medicine in larger or smaller amounts or for longer than recommended. If you use too much Isochron, it might stop working as well in controlling your condition.

Try to rest or stay seated when you take this medicine (may cause dizziness or fainting).

To prevent angina attacks, Isochron is usually taken at regular intervals.

To treat an angina attack that has already begun, use the medicine at the first sign of chest pain. Place the tablet under your tongue and allow it to dissolve slowly. Do not chew or swallow it.

You may use the sublingual tablet within 15 minutes before an activity you think might cause chest pain. Follow your doctor's instructions.

Do not crush, chew, break, or open an extended-release capsule or tablet. Swallow it whole.

Follow your doctor's dosing instructions very carefully. If your doctor changes your brand, strength, or type of isosorbide dinitrate, your dosage needs may change. Ask your pharmacist if you have any questions about the new kind of isosorbide dinitrate you receive at the pharmacy.

Seek emergency medical attention if your chest pain gets worse or lasts longer than 5 minutes, especially if you have trouble breathing or feel weak, dizzy, or nauseated, or lightheaded.

You may have very low blood pressure while taking this medicine. Call your doctor if you are sick with vomiting or diarrhea, or if you are sweating more than usual. Prolonged illness can lead to a serious electrolyte imbalance, making it dangerous for you to use Isochron.

If you take Isochron on a regular schedule to prevent angina, do not stop taking it suddenly or you could have a severe attack of angina. Keep this medicine on hand at all times. Get your prescription refilled before you run out of medicine completely.

Store at room temperature, away from moisture, heat, and light. Keep the bottle tightly closed when not in use.

You should not use Isochron if:

• you are allergic to Isochron, isosorbide mononitrate, or nitroglycerin; or

• you have early signs of a heart attack (chest pain or pressure, pain spreading to your jaw or shoulder, nausea, sweating).

You should not take erectile dysfunction medicine (Viagra, Cialis, Levitra, Stendra, Staxyn, sildenafil, avanafil, tadalafil, vardenafil) while you are taking Isochron. Taking these medicines together can cause a sudden and serious decrease in blood pressure.

To make sure Isochron is safe for you, tell your doctor if you have:

• congestive heart failure;

• kidney disease; or

• low blood pressure.

It is not known whether Isochron will harm an unborn baby. Tell your doctor if you are pregnant or plan to become pregnant.

It is not known whether isosorbide dinitrate passes into breast milk or if it could affect the nursing baby. Tell your doctor if you are breast-feeding.

Since Isochron is sometimes used only when needed, you may not be on a dosing schedule. If you are on a schedule, take the missed dose as soon as you remember. Skip the missed dose if your next dose is less than 2 hours away.

If you are using the extended-release capsule or tablet and your next dose is less than 6 hours away, skip the missed dose and use the medicine at your next regularly scheduled time.

Do not use extra medicine to make up a missed dose.

Seek emergency medical attention if you think you have used too much of Isochron. An overdose of isosorbide dinitrate can be fatal.

Overdose symptoms may include a severe throbbing headache, fever, confusion, severe dizziness, fast or pounding heartbeats, vision problems, nausea, vomiting, stomach pain, bloody diarrhea, trouble breathing, sweating, cold or clammy skin, fainting, and seizure (convulsions).

This medicine may impair your thinking or reactions. Be careful if you drive or do anything that requires you to be alert. Avoid getting up too fast from a sitting or lying position, or you may feel dizzy. Get up slowly and steady yourself to prevent a fall.

Avoid drinking alcohol. Alcohol may increase certain side effects of isosorbide dinitrate (dizziness, drowsiness, feeling light-headed, or fainting).

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

Isochron may cause serious side effects. Call your doctor at once if you have:

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

• worsening angina pain;

• fast or slow heart rate; or

• pounding heartbeats or fluttering in your chest.

Isochron can cause severe headaches. These headaches may gradually become less severe as you continue to use nitroglycerin. Do not stop taking Isochron to avoid headaches. Ask your doctor before using any headache pain medication.

Common side effects may be more likely to occur, such as:

• headache; or

• flushing (warmth, redness, or tingly feeling).

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.

Taking Isochron with certain other medicines can cause severely low blood pressure. This includes medicine to treat erectile dysfunction or pulmonary arterial hypertension. Serious, life-threatening side effects may occur.

Tell your doctor about all your current medicines and any you start or stop using, especially:

• avanafil (Stendra);

• a diuretic or "water pill";

• nitroglycerin;

• riociguat (Adempas);

• sildenafil (Viagra, Revatio);

• tadalafil (Cialis, Adcirca); or

• vardenafil (Levitra, Staxyn).

This list is not complete. Other drugs may interact with isosorbide dinitrate, including prescription and over-the-counter medicines, vitamins, and herbal products. Not all possible interactions are listed in this medication guide.