Nitroglycerin (Glyceryl Trinitrate) 0.2% w/w is a topical formulation, primarily an ointment, used for the prophylaxis and long-term management of angina pectoris. It is a potent organic nitrate that acts as a vasodilator, primarily affecting venous capacitance vessels, reducing preload and myocardial oxygen demand. In the Indian context, it is a cost-effective option for chronic stable angina management, especially in patients who cannot tolerate or afford other long-acting nitrate formulations.
Adult: Apply 1 to 2 inches (2.5 to 5 cm) of ointment, squeezed onto the provided applicator paper, every 8 hours. Start with 0.5 inch, titrate upward based on response and tolerability. Apply to a clean, dry, hairless area of skin (e.g., chest, upper arm, or thigh). Rotate sites to prevent skin irritation.
Note: 1. Measure the desired length on the applicator paper. 2. Squeeze ointment onto paper. 3. Spread thinly (do not rub in vigorously) over a 6x6 inch area. 4. Cover with plastic wrap if directed to enhance absorption. 5. Wash hands thoroughly after application. 6. Remove previous application before applying a new dose. 7. Maintain a daily nitrate-free interval of 10-12 hours (e.g., overnight).
Nitroglycerin is converted to nitric oxide (NO) within vascular smooth muscle cells. 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.
Pregnancy: Category C (US FDA). Animal studies show risk, human data inadequate. Use only if potential benefit justifies potential fetal risk. Avoid during labor as it may interfere with uterine contractility.
Driving: May cause dizziness, lightheadedness, or syncope. Patients should not drive or operate machinery until they know how the medication affects them, especially during initiation and dose titration.
| Phosphodiesterase-5 Inhibitors (Sildenafil, Tadalafil, Vardenafil) | Profound, life-threatening hypotension | Contraindicated |
| Other Vasodilators (e.g., ACE inhibitors, ARBs, Calcium channel blockers, Alpha-blockers) | Additive hypotensive effect | Major |
| Antihypertensives | Enhanced blood pressure lowering | Major |
| Heparin | Nitroglycerin may partially antagonize anticoagulant effect of heparin | Moderate |
| Alcohol | Additive vasodilation and hypotension | Major |
| Ergot Alkaloids (e.g., Ergotamine) | May antagonize the antianginal effect of nitrates and increase ergot-induced vasoconstriction | Moderate |
| Triptans (e.g., Sumatriptan) | Theoretical risk of coronary vasospasm; use with caution | Moderate |
Same composition (Nitroglycerin (0.2% w/w)), different brands: