1. Clinical Overview
Nitroglycerin (2.6mg) is a sublingual tablet formulation of an organic nitrate, primarily used for the acute relief of angina pectoris attacks. It is a potent vasodilator, with its effects predominantly on venous capacitance vessels, leading to reduced preload and myocardial oxygen demand. The 2.6mg strength is a common standard dose for sublingual administration in the Indian market, providing rapid symptomatic relief.
| Onset | Duration | Bioavailability |
|---|---|---|
| 1 to 3 minutes | 30 to 60 minutes | Approximately 40-50% (sublingual), but highly variable due to extensive first-pass metabolism if swallowed. |
2. Mechanism of Action
Nitroglycerin is a prodrug that is enzymatically 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.
3. Indications & Uses
- Acute relief of an attack or prophylaxis of angina pectoris due to coronary artery disease.
- Management of acute coronary syndromes (as part of a broader regimen).
4. Dosage & Administration
Adult Dosage: One 2.6mg tablet placed under the tongue at the onset of an angina attack. Dose may be repeated every 5 minutes if pain persists, up to a maximum of 3 tablets in 15 minutes. For prophylaxis, one tablet 5-10 minutes before anticipated exertion.
Administration: Patient should sit or lie down before taking the tablet. Place tablet under the tongue and allow it to dissolve completely. Do not chew, crush, or swallow. Avoid eating, drinking, or smoking until tablet is fully dissolved. If pain is unrelieved after 3 tablets, seek emergency medical attention immediately.
5. Side Effects
Common side effects may include:
- Headache (often throbbing, may be severe)
- Dizziness, lightheadedness
- Flushing
- Hypotension
- Reflex tachycardia
- Nausea
- Weakness
6. Drug Interactions
| Drug | Effect | Severity |
|---|---|---|
| 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 partially antagonize the anticoagulant effect of heparin. | Moderate |
| Dihydroergotamine | Nitroglycerin may increase the bioavailability of dihydroergotamine, increasing its vasoconstrictive effects. | Moderate |
| Antihypertensives | Potentiated blood pressure lowering. | Major |
| Tricyclic Antidepressants (TCAs) | May potentiate hypotension. | Moderate |
| Aspirin | Increased nitroglycerin bioavailability and enhanced hemodynamic effects. | Moderate |
7. Patient Counselling
- DO sit or lie down before taking the tablet.
- DO place the tablet under your tongue and let it dissolve completely.
- DO use it at the first sign of chest pain or 5-10 minutes before activity that causes angina.
- DO seek emergency help if pain is not relieved after 3 tablets in 15 minutes.
- DO store tablets in their original glass container, tightly closed, away from heat, light, and moisture.
- DONT chew, crush, or swallow the tablet.
- DONT use it with drugs for erectile dysfunction (e.g., Viagra, Cialis).
- DONT consume alcohol while on this medication.
- DONT transfer tablets to plastic or metal containers.
8. Toxicology & Storage
Overdose: Severe hypotension with reflex tachycardia, throbbing headache, dizziness, syncope, palpitations, visual disturbances, flushing, perspiration, cold and clammy skin, nausea, vomiting, diarrhea, dyspnea, methemoglobinemia (cyanosis, chocolate-brown blood, dyspnea, headache, fatigue), coma, and death due to circulatory collapse.
Storage: Store in the original amber glass container with the cotton plug, tightly closed. Protect from moisture, light, and heat. Do not store in bathroom or car. Keep at room temperature (15-30°C). Do not transfer to other containers. Discard any tablets that are discolored, broken, or do not fizzle slightly under the tongue. Replace supply every 6 months after opening to ensure potency.