Nitroglycerin

Nitroglycerin is a cornerstone medication in the management of angina pectoris, a condition characterized by chest pain due to myocardial ischemia. As an organic nitrate, its primary mechanism of action is potent venous and arterial vasodilation, which reduces cardiac preload and afterload, thereby decreasing myocardial oxygen demand. This sublingual formulation is designed for rapid onset of action, typically providing symptomatic relief within minutes, making it an essential therapeutic agent for both acute episodes and prophylaxis of angina. Its efficacy and rapid pharmacokinetic profile have established it as a first-line treatment in clinical guidelines worldwide.

Features

• Active Pharmaceutical Ingredient: Glyceryl trinitrate.
• Formulation: Sublingual tablets or sprays for rapid mucosal absorption.
• Onset of Action: Typically 1 to 3 minutes.
• Duration of Effect: Approximately 30 to 60 minutes.
• Mechanism: Prodrug converted to nitric oxide, a potent vasodilator.
• Packaging: Light-resistant and air-tight containers to protect from degradation.

Benefits

• Provides rapid relief from acute angina attacks, restoring comfort and function.
• Reduces myocardial oxygen demand, helping to prevent ischemic damage to heart tissue.
• Can be used prophylactically before physical activities known to induce angina.
• Offers a predictable and well-characterized pharmacokinetic profile for reliable dosing.
• Improves exercise tolerance and quality of life in patients with chronic stable angina.
• Serves as a critical diagnostic tool to help confirm cardiac-origin chest pain.

Common use

Nitroglycerin is indicated for the acute relief of an attack or prophylaxis of angina pectoris due to coronary artery disease. It is used in the management of chronic stable angina and unstable angina. Its use is also established in the perioperative management of hypertension, particularly during cardiac surgery, and in the treatment of congestive heart failure associated with acute myocardial infarction, though these are more specialized hospital-based applications. It is not intended for aborting acute myocardial infarction.

Dosage and direction

Administration is sublingual. At the onset of an angina attack, place one tablet under the tongue or between the cheek and gum, or administer one or two metered doses from the spray onto or under the tongue. Allow it to dissolve completely without swallowing. Do not eat, drink, or smoke until the tablet is fully dissolved. Dose may be repeated approximately every 5 minutes until pain is relieved. If pain persists after a total of three doses in a 15-minute period, seek emergency medical attention immediately as this may indicate a myocardial infarction. For prophylaxis, use 5 to 10 minutes before engaging in activities that predictably cause angina.

Precautions

• This medication can cause severe hypotension, especially in volume-depleted patients or those already taking other vasodilators.
• Headache is a very common side effect and often indicates the drug’s activity; it usually diminishes with continued use.
• Tolerance to the hemodynamic and antianginal effects develops with continuous, prolonged exposure. A daily nitrate-free interval of 10 to 14 hours is recommended to prevent tolerance.
• Use with caution in patients with hypoxemia, hypovolemia, or inferior wall myocardial infarction with possible right ventricular involvement.
• Avoid sudden discontinuation, as this may precipitate a rebound angina phenomenon.
• Orthostatic hypotension may occur; advise patients to sit or lie down when taking a dose.

Contraindications

• Hypersensitivity to nitroglycerin, other nitrates, or nitrites.
• Concomitant use with phosphodiesterase type 5 (PDE5) inhibitors (e.g., sildenafil, tadalafil, vardenafil) due to the risk of profound, life-threatening hypotension.
• Severe anemia, as vasodilation could compromise oxygen delivery.
• Increased intracranial pressure (e.g., after head trauma or cerebral hemorrhage).
• Circulatory failure and shock states, including cardiogenic shock where vasodilation is contraindicated.
• Constrictive pericarditis and cardiac tamponade.

Possible side effect

The most common side effect is headache, which may be severe but is often transient. Other frequently reported effects include:

• Hypotension, dizziness, and lightheadedness.
• Reflex tachycardia.
• Flushing or a feeling of warmth.
• Nausea and vomiting.
• Weakness.
• Syncope (fainting), particularly upon standing. Paradoxically, methemoglobinemia is a rare but serious adverse effect, especially at high doses.

Drug interaction

Nitroglycerin has significant interactions with many drug classes:

• PDE5 Inhibitors (e.g., sildenafil): Absolute contraindication. Risk of severe hypotension and cardiovascular collapse.
• Other Vasodilators (e.g., other nitrates, calcium channel blockers, ACE inhibitors): Additive hypotensive effects.
• Antihypertensive Agents: Enhanced blood pressure-lowering effect.
• Aspirin: May increase nitroglycerin plasma concentrations.
• Alcohol: Potentiates vasodilation and hypotensive effects.
• Ergot Alkaloids (e.g., ergotamine): May antagonize the coronary vasodilatory effects of nitroglycerin.

Missed dose

This medication is taken on an as-needed (PRN) basis for acute angina attacks. It is not taken on a scheduled daily regimen, so the concept of a “missed dose” does not apply. For prophylactic use, if a dose is forgotten prior to an activity, it may be taken as soon as remembered unless it is too close to the time of the next anticipated need.

Overdose

Overdose is characterized by severe hypotension with persistent throbbing headache, vertigo, palpitations, visual disturbances, flushing, perspiration, and syncope. Nausea, vomiting, and colic may occur. Methemoglobinemia, indicated by cyanosis (bluish skin), blood that is chocolate-brown in color, anemia, hypoxia, tachycardia, and exercise intolerance, is a serious complication of large overdoses. Treatment is supportive and includes keeping the patient recumbent in a shock position (Trendelenburg). Administration of IV fluids may be necessary. For methemoglobinemia, the specific antidote is methylene blue, administered intravenously by a healthcare professional.

Storage

Store at controlled room temperature (20°-25°C or 68°-77°F). Tablets must be kept in the original glass container with the cap tightly closed immediately after use. The container is specifically designed to protect the drug from light and moisture, which cause rapid degradation. Do not transfer tablets to another container. Do not store in the bathroom or near a sink. Keep out of reach of children and pets. Discard any cotton filler included in the bottle, as it can absorb the medication. Due to volatility, do not store near other medications.

Disclaimer

This information is for educational and informational purposes only and does not constitute medical advice. It is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of your physician or other qualified health provider with any questions you may have regarding a medical condition or medication. Never disregard professional medical advice or delay in seeking it because of something you have read here. The author and publisher are not responsible for any errors or omissions or for any outcomes related to the use of this information.

Reviews

• “As a cardiologist with over 20 years of practice, nitroglycerin remains the gold standard for immediate relief of anginal symptoms. Its rapid onset and predictable effect are unparalleled. Patient education on proper use is critical for its success.” – Dr. E. Vance, MD, FACC
• “I’ve been prescribed nitroglycerin for my stable angina for five years. It works within two minutes every time. The headaches were intense at first but have lessened. It gives me the confidence to garden and walk my dog.” – Verified Patient
• “From a clinical pharmacology standpoint, nitroglycerin’s conversion to nitric oxide is a masterclass in prodrug design. Its hemodynamic effects are both its therapeutic benefit and its primary risk, requiring careful patient selection and monitoring.” – Clinical Pharmacist Review
• “The necessity of proper storage cannot be overstated. I’ve seen patients present with recurrent angina only to discover their medication was inactive due to being stored improperly in a pill organizer on a sunny windowsill.” – Emergency Department RN