Action And Clinical Pharmacology: The principal action of Nitrong (nitroglycerin) is that of all nitrates, namely relaxation of vascular smooth muscle. Nitrates act primarily by reducing myocardial oxygen demands rather than increasing its oxygen supply. This effect is thought to be brought about predominantly by peripheral action. Although venous effects predominate, nitroglycerin produces, in a dose-related manner, dilation of both arterial and venous beds. Dilatation of postcapillary vessels, including large veins, promotes peripheral pooling of blood, decreases venous return to the heart, reducing left ventricular end-diastolic pressure (preload). Arteriolar relaxation reduces systemic vascular resistance and arterial pressure (afterload). Left ventricular end-diastolic pressure and volume are decreased, resulting in reduction of ventricular size and wall tension. The reduction in ventricular wall tension results in a net decrease in myocardial oxygen consumption and a favorable net balance between myocardial oxygen supply and demand.
Studies in patients with angina have demonstrated that when given orally in adequate dosage, nitroglycerin has significant vasodilator activity (lasting approximately 8 hours) and improves exercise tolerance. Additional evidence that nitroglycerin is absorbed when given orally is provided by studies in which this agent improved cardiac performance for several hours in patients with severe intractable chronic congestive heart failure.
Indications And Clinical Uses: For the prevention of attacks of angina pectoris associated with chronic angina of effort.
Contra-Indications: Patients with severe anemia, increased intraocular pressure, increased intracranial pressure and hypotension. Known idiosyncrasy to organic nitrates.
Manufacturers’ Warnings In Clinical States: Data on the safe use of nitroglycerin during the early phase of myocardial infarction (the period during which clinical and laboratory findings are unstable) are insufficient to establish safety. The use of nitroglycerin in patients with congestive heart failure requires careful clinical and/or hemodynamic monitoring. Nitrate dependence may occur in patients with chronic use. To avoid possible withdrawal effect, which is a characteristic of vasodilators of the nitrate class, the administration of nitroglycerin should be gradually reduced over a period of 4 to 6 weeks. In industry workers continuously exposed to nitrates, chest pain, acute myocardial infarction and even sudden death have occurred during temporary withdrawal of nitrate exposure.
Precautions: Headaches or symptoms of hypotension, such as weakness or dizziness, particularly when arising suddenly from a recumbent position may be due to overdosage. When they occur, the dose should be reduced or the use discontinued.
Nitroglycerin is a potent vasodilator and causes a slight decrease in mean blood pressure (approximately 10 to 15 mmHg) in some patients when used in therapeutic dosages. Caution should be used in dispensing nitroglycerin in patients who are prone to, or who might be affected by hypotension. Nitrong-SR tablets are not intended for immediate relief of acute attacks of angina pectoris. Sublingual nitroglycerin preparations should be used for this purpose.
Tolerance to this drug and cross tolerance to other nitrates or nitrites may occur.
Adverse Reactions: Headache is the most common side effect which can be treated with mild analgesics. If headache is unresponsive to such treatment, the dose should be reduced or its use discontinued.
Less frequently, postural hypotension, an increase in heart rate, faintness, flushing, dizziness, nausea, vomiting and dermatitis have been reported.
Symptoms And Treatment Of Overdose: Symptoms: Primarily related to vasodilation including cutaneous flushing, headache, nausea, dizziness and hypotension; methemoglobinemia is also possible.
Treatment: No specific antidote is available. Treatment should be symptomatic and supportive.
Dosage: Adults: Recommended initial dosage is 1 tablet 3 times a day before breakfast, late afternoon before a meal and before retiring. Dosage may be increased progressively up to 2 tablets 3 times a day.
Availability And Storage: Each oral sustained-release tablet contains: nitroglycerin 2.6 mg. Nonmedicinal ingredients: alcohol, calcium stearate, D&C Yellow No. 10 aluminum lake, dicalcium phosphate, iron oxide, shellac, starch, sucrose and talc. Bottles of 100 and 1 000. (Shown in Product Recognition Section)
NITRONG® SR Rhône-Poulenc Rorer Nitroglycerin Antianginal