Nitroglycerin Injection is indicated for the management of perioperative hypertension, for controlling congestive heart failure associated with acute myocardial infarction, for treating angina pectoris in patients unresponsive to sublingual nitroglycerin and beta-blockers, and for inducing intraoperative hypotension.

Nitroglycerin primarily acts by relaxing vascular smooth muscle, leading to dilation of peripheral arteries and veins. Venous dilation causes pooling of blood in the peripheral circulation and reduces venous return to the heart, thereby decreasing left ventricular end-diastolic pressure and pulmonary capillary wedge pressure (preload). Arterial dilation lowers systemic vascular resistance, systolic blood pressure, and mean arterial pressure (afterload). Additionally, nitroglycerin also causes dilation of the coronary arteries.

Not for direct intravenous injection. Nitroglycerin injection is a highly concentrated and potent medication that must be diluted with either 5% dextrose injection or 0.9% sodium chloride injection before infusion. It should not be mixed with other medications.

Initial Dilution: Using aseptic technique, transfer the contents of one nitroglycerin ampoule (containing 50 mg nitroglycerin) into a 500 mL glass bottle of either 5% dextrose injection or 0.9% sodium chloride injection. This results in a final concentration of 100 mcg/mL.

Maintenance Dilution: When selecting the appropriate dilution, consider the patient’s fluid requirements and the expected duration of infusion. After initial dose titration, the solution concentration may be increased if necessary to minimize fluid volume. However, the concentration should not exceed 400 mcg/mL.

The vasodilatory effect of nitroglycerin may be enhanced when used with other vasodilators. Administering nitroglycerin infusion through the same infusion line as blood may cause pseudoagglutination and hemolysis. Generally, nitroglycerin in 5% dextrose or 0.9% sodium chloride solution should not be mixed with other medications. Intravenous nitroglycerin may reduce the anticoagulant effect of heparin in some patients. Therefore, in patients receiving both intravenous nitroglycerin and heparin, frequent monitoring of activated partial thromboplastin time (aPTT) is recommended to guide therapy.

Allergic reactions to organic nitrates are rare but may occur. Nitroglycerin injection is contraindicated in patients with known hypersensitivity to nitrates. It is also contraindicated in patients with pericardial tamponade, restrictive cardiomyopathy, or constrictive pericarditis, where cardiac output depends on venous return.

Adverse effects of nitroglycerin are generally dose-dependent and mainly related to its vasodilatory action. Headache is the most commonly reported side effect and may be severe or recurrent, especially at higher doses. Episodes of lightheadedness may occur, sometimes associated with changes in blood pressure. Hypotension is less common but may occasionally be severe enough to require discontinuation of therapy. Syncope, worsening angina (crescendo angina), and rebound hypertension have been reported but are uncommon. Very rarely, standard doses of organic nitrates may cause methemoglobinemia in otherwise healthy individuals. However, this condition is extremely rare at usual therapeutic doses.

Pregnancy category C. It is not known whether nitroglycerin is excreted in human breast milk. Since many drugs are excreted in breast milk, caution should be exercised when administering nitroglycerin injection to nursing mothers.

Severe hypotension and shock may occur even with small doses of nitroglycerin. Therefore, it should be used cautiously in patients who are volume-depleted or already hypotensive. Hypotension caused by nitroglycerin may be accompanied by paradoxical bradycardia and worsening angina. Nitrate therapy may aggravate angina in patients with hypertrophic cardiomyopathy. As tolerance to nitrates develops, the effect of sublingual nitroglycerin on exercise tolerance may be reduced, though still present. In individuals with long-term exposure to high doses of organic nitrates, tolerance may develop. During withdrawal, symptoms such as chest pain, acute myocardial infarction, and even sudden death have been reported, indicating possible physical dependence.

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

The toxic effects of nitroglycerin overdose are mainly due to its vasodilatory action, leading to venous pooling, decreased cardiac output, and hypotension. These hemodynamic changes may present with various symptoms, including increased intracranial pressure (with persistent throbbing headache, confusion, and moderate fever), dizziness, palpitations, visual disturbances, nausea and vomiting (sometimes with colic or even bloody diarrhea), and fainting (especially in an upright position). Patients may also experience air hunger and shortness of breath, followed by reduced respiratory effort. Sweating may occur, with the skin appearing flushed or cold and clammy. Other severe effects include heart block, bradycardia, paralysis, coma, seizures, and even death.

Nitrates: Coronary vasodilators

Store below 30°C, protected from light and moisture. Keep out of the reach of children.