📋 Clinical Overview

Nitroglycerin is a potent organic nitrate vasodilator, primarily used for the prophylaxis and treatment of angina pectoris. It acts by relaxing vascular smooth muscle, leading to venous and arterial dilation. This reduces myocardial oxygen demand (by decreasing preload and afterload) and improves oxygen supply (by dilating coronary arteries). The 2.5mg strength is typically formulated as a sublingual tablet for rapid relief of acute anginal attacks.

💊 Dosage & Administration

Adult: For acute angina: 2.5mg tablet placed under the tongue at the first sign of an attack. Dose may be repeated every 5 minutes if pain persists, up to a maximum of 3 tablets in 15 minutes. For prophylaxis: 2.5mg sublingually 5-10 minutes before anticipated physical or emotional stress.

Note: Patient should be SITTING DOWN when taking the first dose. Place tablet under the tongue and allow it to dissolve completely. Do not chew, crush, or swallow. Avoid eating, drinking, or smoking until tablet dissolves. If pain is not relieved after 3 doses in 15 minutes, seek emergency medical attention immediately.

⚠️ Contraindications

Hypersensitivity to nitrates, nitrites, or any component
Concurrent use with phosphodiesterase-5 inhibitors (e.g., Sildenafil, Tadalafil, Vardenafil) due to risk of severe hypotension
Severe anemia
Increased intracranial pressure (e.g., head trauma, cerebral hemorrhage)
Cardiac tamponade, constrictive pericarditis

🔬 Mechanism of Action

Nitroglycerin is converted to nitric oxide (NO) within vascular smooth muscle cells, primarily by mitochondrial aldehyde dehydrogenase (ALDH2) in veins and arteries. NO activates soluble guanylyl cyclase, increasing intracellular cyclic guanosine monophosphate (cGMP). Elevated cGMP leads to dephosphorylation of myosin light chains, resulting in smooth muscle relaxation and vasodilation.

🤕 Side Effects

Headache (often throbbing, may be severe initially)
Dizziness, lightheadedness
Flushing
Hypotension, postural hypotension
Reflex tachycardia
Nausea, vomiting

🤰 Special Populations

Pregnancy: Category C (US FDA). Animal studies show adverse effects. Use only if potential benefit justifies potential risk to the fetus. Avoid during labor and delivery as it may interfere with uterine contractility.

Driving: May cause dizziness, lightheadedness, or syncope, especially after the first dose. Patients should not drive or operate machinery until they know how the drug affects them.

🔄 Drug Interactions

Phosphodiesterase-5 Inhibitors (Sildenafil, Tadalafil, Vardenafil)	Profound, life-threatening hypotension	Contraindicated
Other Vasodilators (ACE inhibitors, ARBs, Calcium channel blockers, Alpha-blockers)	Additive hypotensive effect	Major
Alcohol	Enhanced vasodilation and hypotension	Major
Heparin	Nitroglycerin may decrease anticoagulant effect of heparin	Moderate
Dihydroergotamine	Nitroglycerin may increase ergotamine bioavailability, increasing vasoconstrictive effects	Moderate
Antihypertensives	Additive blood pressure lowering	Moderate
Tricyclic Antidepressants (TCAs)	May exacerbate hypotension	Moderate

Cardinol