Nitroglycerin PO

Reviewed on 4/7/2022

What Is Nitroglycerin PO and How Does It Work?

Nitroglycerin PO is a prescription medication used for the prevention of angina pectoris.

Nitroglycerin PO is available under the following different brand names: Glyceryl trinitrate PO

What Are Dosages of Nitroglycerin PO?

Adult dosage

Capsule, extended-release 

  • 2.5mg
  • 6.5mg
  • 9mg

Angina Pectoris (Prophylaxis)

Adult and geriatric dosage

  • ER capsule: Initial 2.5-6.5 mg orally every 6-8 hours.

Dosage Considerations – Should be Given as Follows: 

  • See “Dosages”

What Are Side Effects Associated with Using Nitroglycerin PO?

Common side effects of Nitroglycerin PO include:

  • headache,
  • dizziness,
  • numbness,
  • tingling, and
  • burning pain.

Serious side effects of Nitroglycerin PO include:

  • severe or throbbing headaches,
  • pounding heartbeats,
  • fluttering in the chest,
  • slow heart rate,
  • lightheadedness,
  • blurred vision,
  • dry mouth,
  • chest pain or pressure,
  • pain spreading to the jaw or shoulder,
  • nausea, and
  • sweating

Rare side effects of Nitroglycerin PO include:

  • none 

This is not a complete list of side effects and other serious side effects or health problems that may occur as a result of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

What Other Drugs Interact with Nitroglycerin PO?

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist of all the products you use. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your health care professional or doctor for additional medical advice, or if you have health questions, concerns.

What Are Warnings and Precautions for Nitroglycerin PO?


  • Hypersensitivity, acute MI, severe anemia
  • Recent use (within several days) of PDE-5 inhibitors (e.g., avanafil, sildenafil, tadalafil, or vardenafil) may cause dangerously low hypotension; the time course of the interaction appears to be related to the PDE-5 inhibitor half-life
  • Coadministration with soluble guanylate cyclase stimulators, including riociguat

Effects of drug abuse

  • None

Short-Term Effects

  • See “What Are Side Effects Associated with Using Nitroglycerin PO?”

Long-Term Effects

  • See “What Are Side Effects Associated with Using Nitroglycerin PO?”


  • Use caution in increased ICP (e.g., head trauma, cerebral hemorrhage; potential contraindication), hyperthyroidism, increased IOP, postural hypotension, volume depletion, low systolic BP
  • Do not change brands unintentionally as not all are bioequivalent
  • Treat drug-induced headache with aspirin or acetaminophen
  • Provide nitrate-free intervals (10-12 hours or overnight) to avoid the development of tolerance
  • Angina long term prophylaxis, NOT for acute relief
  • Lack of burning/tingling does not indicate loss of potency
  • Discontinue if blurred vision occurs
  • Use supportive treatment in overdose
  • Benefits of oral nitroglycerin in patients with acute myocardial infarction or congestive heart failure not established; if administered in these conditions, use careful clinical or hemodynamic monitoring to avoid hazards of hypotension and tachycardia; because effects of capsules are so difficult to terminate rapidly, not recommended in these settings
  • Severe hypotension, particularly with upright posture, may occur with even small doses; should be used with caution in patients who may be volume depleted or who, for whatever reason, are already hypotensive; hypotension induced by therapy may be accompanied by paradoxical bradycardia and increased angina pectoris
  • Therapy may aggravate angina caused by hypertrophic cardiomyopathy
  • As tolerance to other forms of nitroglycerin develops, the effect of sublingual nitroglycerin on exercise tolerance, although still observable, is somewhat blunted
  • In industrial workers who have had long-term exposure to unknown (presumably high) doses of organic nitrates, tolerance occurs; chest pain, acute myocardial infarction, and even sudden death have occurred during temporary withdrawal of nitrates from these workers, demonstrating the existence of true physical dependence
  • Some clinical trials in angina patients have provided nitroglycerin for about 12 continuous hours of every 24-hour day; during nitrate-free intervals in some of these trials, anginal attacks have been more easily provoked than before treatment, and patients have demonstrated hemodynamic rebound and decreased exercise tolerance; the importance of these observations not known

Pregnancy and Lactation

  • Use with caution if benefits outweigh the risks during pregnancy
  • Lactation
    • Not known whether the drug crosses into breast milk, use caution
Medscape. Nitroglycerin PO.

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