Nitroglycerin is a cornerstone medication in the management of angina pectoris, a condition characterized by chest pain due to coronary artery disease. As an organic nitrate vasodilator, its primary mechanism of action is the relaxation of vascular smooth muscle, leading to a reduction in cardiac preload and afterload. This significantly decreases myocardial oxygen demand, providing both immediate symptomatic relief during acute angina attacks and prophylactic protection against anticipated episodes. Available in sublingual, oral spray, ointment, and transdermal patch formulations, nitroglycerin remains an essential, fast-acting therapeutic option in cardiology for enhancing functional capacity and quality of life in eligible patients.

Features

• Active pharmaceutical ingredient: Glyceryl trinitrate.
• Multiple administration routes: sublingual tablets, transmucosal spray, topical ointment, and extended-release transdermal patches.
• Rapid onset of action, typically within 1 to 3 minutes for sublingual and spray formulations.
• Short duration of effect for acute formulations; prolonged effect available via sustained-release systems.
• Metabolized systemically to release nitric oxide (NO), a potent vasodilator.
• Standardized dosing ensures predictable pharmacokinetic and pharmacodynamic profiles.

Benefits

• Provides rapid relief from the pain and discomfort of acute angina attacks.
• Reduces cardiac workload and myocardial oxygen consumption, preventing ischemic episodes.
• Can be used prophylactically before physical exertion or stressful events known to trigger angina.
• Improves exercise tolerance and overall functional capacity in patients with chronic stable angina.
• Offers flexible dosing options to suit individual patient needs and lifestyles.
• Contributes to an improved quality of life by reducing the frequency and severity of angina symptoms.

Common use

Nitroglycerin is primarily indicated for the treatment and prevention of angina pectoris attacks. Its use is standard in patients with diagnosed coronary artery disease (CAD), including those with stable exertional angina and vasospastic (Prinzmetal’s) angina. The sublingual tablet and spray formulations are first-line for the immediate relief of acute angina pain. The topical ointment and transdermal patch systems are used for longer-term prophylaxis to reduce the frequency of attacks. It is not intended for the abortive treatment of other types of chest pain (e.g., non-cardiac) and should only be used under a confirmed diagnosis and prescription from a healthcare provider.

Dosage and direction

Dosing is highly formulation-specific and must be individualized under medical supervision.

• Sublingual Tablets: At the first sign of an attack, place one tablet (typically 0.3 mg or 0.4 mg) under the tongue or in the buccal pouch. Allow it to dissolve completely without swallowing. Dose may be repeated every 5 minutes for a maximum of 3 tablets within a 15-minute period. If pain persists after 3 doses, seek emergency medical attention immediately.
• Translingual Spray: Spray one or two metered doses (typically 0.4 mg per dose) onto or under the tongue. Do not inhale the spray. Close mouth immediately after administration. Do not rinse mouth for 5-10 minutes. The same repeating and emergency guidelines as sublingual tablets apply.
• Ointment: Apply a measured dose (in inches) using the supplied applicator paper to a clean, hairless area of skin (e.g., chest, arm). Do not rub in. Cover with plastic wrap if desired. Rotate application sites to prevent skin irritation. Usually applied every 3-8 hours, with a nitrate-free interval to prevent tolerance.
• Transdermal Patch: Apply one patch (delivering 0.2-0.8 mg/hour) to a clean, dry, hairless area of skin. Remove after 12-14 hours to allow for a 10-12 hour nitrate-free interval, typically overnight, to maintain efficacy.

General Direction: Always sit down before taking a dose to minimize the risk of hypotension and dizziness. Do not abruptly stop long-term therapy.

Precautions

• Hypotension: Nitroglycerin can cause severe hypotension, especially in volume-depleted patients. Caution is advised in patients with pre-existing low blood pressure.
• Tolerance: Continuous, 24-hour exposure leads to tolerance (loss of hemodynamic and antianginal effects). A daily nitrate-free interval of 10-12 hours is mandatory for patch and ointment formulations.
• Headache: A common, often severe, headache is a frequent side effect that usually diminishes with continued therapy. Do not use analgesics prophylactically without consulting a physician.
• Conditional Use: Use with caution in patients with hypertrophic cardiomyopathy (HOCM), as it may exacerbate outflow tract obstruction. Caution is also advised in patients with inferior wall myocardial infarction and right ventricular involvement.
• Storage: Protect tablets and spray from light, moisture, and heat. Do not carry tablets in a pill organizer; keep them in their original dark glass bottle. Replace sublingual tablets every 6 months after opening the bottle to ensure potency.

Contraindications

• Known hypersensitivity to nitroglycerin, other nitrates, or nitrites.
• Concomitant use with phosphodiesterase-5 (PDE-5) inhibitors (e.g., sildenafil, tadalafil, vardenafil) due to the risk of profound, life-threatening hypotension.
• Use of riociguat (a soluble guanylate cyclase stimulator).
• Severe anemia.
• Increased intracranial pressure (e.g., due to head trauma, cerebral hemorrhage).
• Circulatory failure and shock, including cardiogenic shock.
• Hypotension (uncorrected low blood pressure).

Possible side effect

The vasodilatory action of nitroglycerin is responsible for most of its side effects, which are often dose-related.

• Very Common (>10%): Headache (may be severe and persistent), dizziness, lightheadedness, orthostatic hypotension.
• Common (1-10%): Tachycardia (reflex), flushing, nausea, vomiting, weakness.
• Uncommon (0.1-1%): Dermatitis or skin irritation (with topical forms), syncope (fainting), paradoxical bradycardia and increased angina pain.
• Rare (<0.1%): Methemoglobinemia (especially with overdose), exfoliative dermatitis, blurred vision, dry mouth.

Drug interaction

Nitroglycerin has significant and potentially dangerous interactions.

• PDE-5 Inhibitors (e.g., Sildenafil, Tadalafil, Vardenafil): Absolute Contraindication. Concomitant use can cause severe hypotension, syncope, myocardial infarction, or stroke.
• Other Vasodilators (e.g., other nitrates, calcium channel blockers, ACE inhibitors): Additive hypotensive effects. Blood pressure must be monitored closely.
• Antihypertensive Agents: Enhanced blood pressure-lowering effect.
• Alcohol: Potentiates vasodilation and hypotension.
• Dihydroergotamine: May decrease the vasoconstrictive effect of dihydroergotamine.
• Heparin: Concomitant intravenous use may reduce the anticoagulant effect of heparin.

Missed dose

This applies primarily to scheduled prophylactic formulations (ointment, patches).

• If you miss a dose of your scheduled nitroglycerin (ointment/patch), apply it as soon as you remember.
• If it is almost time for the next dose, skip the missed dose and resume your regular dosing schedule.
• Do not double the dose to make up for a missed one.
• For as-needed sublingual tablets or spray: this is not applicable, as these are taken only at the time of an attack.

Overdose

Nitroglycerin overdose is a medical emergency characterized by severe hypotension and its sequelae.

• Signs and Symptoms: Profound hypotension with weak pulse, syncope, blurred vision, flushing, diaphoresis (cold sweat), nausea/vomiting, cyanosis with methemoglobinemia (chocolate-brown blood), dyspnea, tachycardia followed by bradycardia, heart palpitations, paralysis, coma, and circulatory collapse.
• Management: Immediately discontinue nitroglycerin. Place patient in a supine position with legs elevated to promote venous return. Administer IV fluids for volume expansion. In cases of severe hypotension, alpha-adrenergic agonists (e.g., phenylephrine) may be considered. For methemoglobinemia (>30% and symptomatic), methylene blue 1-2 mg/kg IV is the specific antidote. Provide standard supportive care, including oxygen and ECG monitoring.

Storage

Proper storage is critical for maintaining the potency of nitroglycerin, especially the sublingual forms.

• Sublingual Tablets: Store in the original dark glass bottle with the cap tightly closed. Protect from light, moisture, and heat. Do not transfer to other containers (e.g., pill organizers). Discard any cotton filler from the bottle. Tablets lose potency quickly; replace the supply every 6 months after opening.
• Spray: Store at room temperature. Do not expose to extreme heat or open flame.
• Ointment & Patches: Store at room temperature.
• Keep all medications out of the reach of children and pets.

Disclaimer

This information is for educational purposes only and 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 before starting any new treatment. Never disregard professional medical advice or delay in seeking it because of something you have read here. The information provided is not exhaustive and may not cover all possible uses, directions, precautions, interactions, or adverse effects.

Reviews

• “As a cardiologist with over 20 years of practice, nitroglycerin remains an irreplaceable tool. Its rapid onset for aborting acute angina is unmatched. Patient education on proper use and the critical nitrate-free interval for patches is paramount for success.” – Dr. A. Reynolds, MD, FACC
• “Diagnosed with CAD 5 years ago. My nitroglycerin spray is my security blanket. It works within a minute when I feel chest tightness coming on after walking uphill. The headaches were rough at first but have mostly subsided.” – Verified Patient
• “The efficacy of sublingual nitroglycerin is entirely dependent on proper storage. I’ve seen too many patients with ineffective medication because it was stored improperly or kept for years. Patient counseling on this point is non-negotiable.” – Clinical Pharmacist
• “The transdermal patch system has significantly improved my father’s quality of life. He applies it in the morning and removes it at night. His angina episodes have reduced from multiple per week to almost zero.” – Caregiver