Nitroglycerin is indicated for the rapid relief of angina attacks or for the prevention of angina pectoris associated with coronary artery disease.

Nitroglycerin, an organic nitrate, acts as a vasodilator affecting both arteries and veins. It is available as a metered-dose spray formulation. Each spray delivers nitroglycerin (400 mcg per spray, 200 metered sprays) as fine droplets administered under the tongue.

Nitroglycerin primarily acts by relaxing vascular smooth muscle, leading to dilation of both peripheral arteries and veins, with a greater effect on the venous system. Expansion of post-capillary vessels, particularly large veins, causes pooling of blood in the periphery and reduces venous return to the heart, thereby lowering left ventricular end-diastolic pressure (preload). Relaxation of arterioles decreases systemic vascular resistance and arterial pressure (afterload).

Nitroglycerin generates nitric oxide (NO), which activates guanylate cyclase and increases cyclic guanosine monophosphate (cGMP) levels in smooth muscle and other tissues. This results in dephosphorylation of myosin light chains, regulating muscle contraction and producing vasodilation.

Absorption: Nitroglycerin is absorbed rapidly, making it suitable for emergency use.
Distribution: The volume of distribution is approximately 3 L/kg.
Metabolism: It is quickly metabolized in the liver into di-nitrate and mono-nitrate compounds.
Elimination: Nitroglycerin is mainly eliminated through the kidneys as di-nitro metabolites.

Sublingual tablet: One tablet (0.5 mg) should be placed under the tongue at the onset of an acute angina attack. The dose may be repeated every 5 minutes until relief is achieved. If symptoms persist after taking 3 tablets within 15 minutes, immediate medical attention is advised.

Sustained release tablet: The dosage should be individualized based on patient response and severity of angina.

• 2.6 mg: One tablet twice daily before meals (morning and noon). If needed, the dose may be gradually increased to 2–3 tablets twice daily.
• 6.4 mg: One tablet twice daily or as prescribed by a physician.

Spray: At the beginning of an angina attack, administer one or two metered sprays under the tongue. The dose may be repeated every 5 minutes if necessary. A maximum of 3 sprays is recommended within a 15-minute period. If chest pain continues after 3 sprays, seek medical help immediately. It may also be used preventively 5–10 minutes before activities that may trigger an attack.

Priming of Nitroglycerin Spray:Before using Nitroglycerin Spray for the first time, it must be primed. Follow these steps:

• Remove the plastic cap from the container.
• Hold the container upright, pointing away from yourself and others. Press the grooved button 5 times.
• The spray is now primed and ready for use.
• If unused for 6 weeks, re-prime by pressing the button once.
• If unused for 3 months, re-prime by pressing the button up to 5 times.

Giving a dose of Nitroglycerin Spray:

• Use the spray while resting and preferably in a sitting position.
• Hold the container upright with your index finger on the grooved button.
• Open your mouth and bring the container close to your mouth.
• Press the grooved button firmly to release the spray under the tongue.
• Release the button and close your mouth immediately. Avoid swallowing right away. Do not spit or rinse your mouth for 5–10 minutes.
• If another dose is required, repeat the steps.
• Replace the plastic cap after use.

Special Instruction:

• Nitroglycerin Spray is for sublingual use only. Do not inhale it.
• Do not exceed more than 3 sprays within 15 minutes.
• Seek emergency medical help if chest pain continues after 3 sprays.
• Do not shake the container.
• Keep away from flames; do not spray near fire.

Patients taking antihypertensive agents, beta-blockers, phenothiazines, or nitrates should be monitored for possible additive blood pressure–lowering effects. Concurrent use of nitrates with alcohol may result in significant hypotension. The vasodilatory and hemodynamic effects of Nitroglycerin may be enhanced when used together with Aspirin.

 Nitroglycerin is contraindicated in patients using PDE5 inhibitors (such as Sildenafil, Vardenafil, and Tadalafil), as well as in those with severe anemia, elevated intracranial pressure, hypersensitivity to nitrates or nitrites, and in cases of acute circulatory failure or shock.

The most commonly reported side effects include headache, flushing, and low blood pressure (hypotension).

There is limited information regarding the safety of nitrates during pregnancy and breastfeeding. Nitroglycerin should only be used in pregnant or lactating women if clearly necessary and prescribed by a physician. It is not known whether Nitroglycerin passes into human breast milk.

The lowest effective dose should be used to control acute angina attacks. Excessive or prolonged use may lead to tolerance. Nitroglycerin should be used cautiously in patients who are volume-depleted or already have low blood pressure.

The safety and effectiveness of nitroglycerin in pediatric patients have not been clearly established.

In cases of accidental or intentional overdose, nitroglycerin toxicity may present with symptoms such as vomiting, restlessness, hypotension, cyanosis, methemoglobinemia, rapid heart rate (tachycardia), and fainting (syncope).

Nitrates: Coronary vasodilators

Keep out of the reach of children. Store in a dry place at temperatures below 25°C and protect from light.