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- What are nitrates (nitrate medications)?
- What are examples of nitrates available in the United States?
- What are the side effects of nitrates?
- Are nitrates safe to take during pregnancy or while breastfeeding?
- What drugs interact with nitrates?
- What formulations of nitrates are available?
- How do nitrates work?
Are nitrates safe to take during pregnancy or while breastfeeding?
- The FDA classifies nitrates as pregnancy category C, which means that safe and effective use of nitrates in pregnant women has not been established. Nitrates should be given to pregnant women only if clearly needed.
- It is not known whether nitrates enter breast milk; therefore, nitrates must be used with caution in women who are breastfeeding.
What drugs interact with nitrates?
- Nitrates can slow down metabolism of cabergoline and ergonovine, resulting in an increase in systolic blood pressure and an increased likelihood of angina symptoms.
- Sildenafil (Viagra), tadalafil (Cialis) and vardenafil (Levitra) increase the blood pressure lowering effects of nitrates and may cause excessive blood pressure reduction. Men taking nitrates should not take sildenafil (Viagra), tadalafil (Cialis), or vardenafil (Levitra).
What preparations of nitrates are available?
Nitrates are available in various formulations. Nitroglycerin is available in:
- oral capsule
- sublingual tablet
- sublingual spray
- intravenous solution
- topical ointment
- topical patch
- isosorbide mononitrate and isosorbide dinitrate are available as immediate and extended-release tablets
Only sublingual tablets, intravenous, or immediate release tablets are used for immediate treatment of angina because the onset of action of the other formulations is not fast enough.
How do nitrates work?
Nitrates are vasodilators (dilators of blood vessels that increase their diameter) that allow blood to flow more easily. Blood returning from the body in the veins must be pumped by the heart through the lungs and into the body's arteries against the high pressure in the arteries. In order to accomplish this work, the heart's muscle must produce and use energy ("fuel"), and this requires consumption of oxygen that is supplied by the blood. Angina (angina pectoris or "heart pain") is due to an inadequate flow of blood (and oxygen) to the muscle of the heart.
Nitrates, including isosorbide dinitrate, increase the flow of blood and oxygen to the heart and thereby increase the amount of work that the heart can do by dilating (expanding) the arteries and veins in the body. Dilation of the veins reduces the amount of blood that returns to the heart that must be pumped, while dilation of the arteries lowers the pressure in the arteries against which the heart must pump. As a consequence of both effects, the heart works less and requires less blood and oxygen.
REFERENCE: FDA Prescribing Information.
Report Problems to the Food and Drug Administration
You are encouraged to report negative side effects of prescription drugs to the FDA. Visit the FDA MedWatch website or call 1-800-FDA-1088.
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