GTN SR is indicated for the prophylaxis of angina pectoris. The onset of action is not sufficiently rapid for this form to be useful in aborting an acute anginal episode.
Nitroglycerin causes relaxation of vascular smooth muscle, producing a vasodilator effect on both peripheral arteries and veins. Dilation of veins promote peripheral pooling of blood and decreases venous return to the heart, thereby reducing left ventricular end-diastolic pressure (preload) and relaxation of arteries reduce systemic vascular resistance and arterial pressure (afterload).
Dosage should always to be adjusted according to the requirement and response obtained by the individual patient and the severity of the anginal pain. For adults, one Nitroglycerin 2.6 mg sustained released tablet or capsule in morning and evening. This should be taken empty stomach.
GTN SR dilates peripheral blood vessels and may increase the antihypertensive properties of vasodilators, calcium antagonists, beta-adrenergic blockers. Concomitant use of nitrates with tricyclic antidepressants and alcohol may cause high blood pressure. Concomitant use of nitrates with phosphodiesterase type 5 (PDE5) inhibitors, such as sildenafil, vardenafil and tadalafil cause fall in blood pressure. Aspirin decreases the clearance and enhances the hemodynamic effects of GTN SR. GTN SR may reduce the pharmacologic effects of heparin when used concomitantly. Nitrates increase the bioavailability of dihydroergotamine.
Nitroglycerin is contraindicated in patients with a known hypersensitivity to nitroglycerin, other organic nitrates, or nitrites or to the excipients of the medicine. It is also contraindicated in patients with acute myocardial infarction, marked anaemia, head trauma, cerebral haemorrhage, or closed angle glaucoma.
Headache may occur at the onset of treatment but will usually subside after a few days. If the headache persists dosage should be decreased. Other side effects include tachycardia, postural hypotension and syncope, cyanosis and methaemoglobinaemia.
There is no evidence relating to the safety of nitrates in pregnancy and lactation. Nitroglycerin should be administered to pregnant women and nursing mothers unless considered essential by the physician.
GTN SR should be used with caution in patients who are predisposed to closed-angle glaucoma. As with other drugs for the treatment of angina pectoris, abrupt discontinuation of therapy may lead to exacerbation of symptoms. When discontinuing long term treatment, the dosage should be reduced gradually over several days, and the patient carefully monitored. The use of GTN SR during the early days of acute myocardial infarction requires particular attention to hemodynamic monitoring and clinical status to avoid the hazards of hypotension and tachycardia.
ln the case of overdosage, the likely symptomatology may be peripheral vasodilation with a fall in blood pressure and reflex tachycardia. In such an event, monitoring of cardiac function and general supportive measures should be used. If not successful, circulating plasma volume should be increased by substitution of fluid. ln life-threatening situations, administration of vasopressors should be considered.
Nitrates: Coronary vasodilators
Store in a cool and dry place away from light and heat. Keep all medicines out of the reach of children.