Nitroglycerin and drugs like it (nitrates) are used to treat heart disease. They are very effective for treating angina. Angina is discomfort in the chest that may come on during exercise and go away with rest. It is usually caused by blockage in the arteries that supply blood to the heart muscle (the coronary arteries). Nitrates are also used to treat heart failure.
Nitroglycerin and nitrates relax and expand (dilate) veins and arteries. Expanding blood vessels has at least two good effects:
By expanding the blood vessels and slightly lowering blood pressure, chest discomfort or pain is quickly relieved.
Three forms are available in the US: nitroglycerin (NTG), isosorbide dinitrate (ISDN), and isosorbide mononitrate (ISMN). All are available in a variety of dosages. Nitrates are available in several forms:
The under-the-tongue and spray forms of NTG act very fast (usually in about 2 minutes), but don't last long (about 20 to 40 minutes). They should be taken when the chest pain or discomfort starts. They can be taken before you start physical activity to prevent chest symptoms from starting. Because the effects of rapid-acting NTG last for only a short time, it is not a good medicine for long-term control of angina.
Nitrates that come in capsules and patches work for a longer time (up to 6 hours). They are used for the long-term control of angina.
Nitroglycerin is the only nitrate now available for use intravenously (by vein). NTG by vein is especially useful for the treatment of unstable angina or for a heart attack.
Nitrates often cause headaches. The headaches usually get better as you continue to take the drugs. Aspirin or acetaminophen tablets can provide relief. Even then, some people will just not be able to take long-acting nitrates because of the headaches. The patch may also cause some itching or a rash on the skin. Nitroglycerin tablets may cause burning or stinging under the tongue.
The nitrates' ability to lower blood pressure may cause problems. Low blood pressure is more likely to happen with the first doses of a nitrate. Fainting spells may occur. Taking the first doses sitting or lying down helps to prevent such problems. Be sure to tell your doctor about any other medicines you are taking because there could be unwanted side effects.
If you use any form of nitrates for a long time, your body gets used to it. The medicine may not work as well as it once did. Nitrates work best when their use is stopped for at least 10 hours during a 24-hour period. Carefully follow your doctor's instructions about taking the medicine.
Doses are different for different people. Your doctor will work with you to find the best dose and schedule for you.
Disclaimer: This content is reviewed periodically and is subject to change as new health information becomes available. The information provided is intended to be informative and educational and is not a replacement for professional medical evaluation, advice, diagnosis or treatment by a healthcare professional.
HIA File MED4269F.HTM Release 9.0/2006
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