Before using isosorbide dinitrate 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 isosorbide dinitrate, 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, isosorbide dinitrate 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 isosorbide dinitrate.
If you take isosorbide dinitrate 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.
 Detailed Isosorbide dinitrate dosage information
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What happens if I miss a dose?
Since isosorbide dinitrate 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.
What happens if I overdose?
Seek emergency medical attention if you think you have used too much of  isosorbide dinitrate. 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).
