Antianginal – Vasodilator
Action And Clinical Pharmacology: The principal action of 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. Dilation of the post-capillary vessels, including large veins, promotes peripheral pooling of blood and decreases venous return to the heart, reducing left ventricular end-diastolic pressure (pre-load). Arteriolar relaxation reduces systemic vascular resistance and arterial pressure (after-load). 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.
When the ointment is spread on the skin, nitroglycerin is continuously absorbed through the skin into the systemic circulation, bypassing portal circulation. Therapeutic effect can be anticipated 15 minutes after application. The duration of action of the ointment has been shown to be approximately 3 to 8 hours.
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. Also, patients with known idiosyncrasy to organic nitrates.
Manufacturers’ Warnings In Clinical States: Data on the safe use of nitroglycerin ointment 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 this ointment 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 effects, the administration of nitroglycerin ointment should gradually be reduced over 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 use of nitroglycerin ointment discontinued.
Nitroglycerin is a potent vasodilator and causes a slight decrease in mean blood pressure (approximately 10 to 15 mm Hg) in some patients when used in therapeutic dosages. Caution should be exercised in using the drug in patients who are prone to, or who might be affected by hypotension.
Nitroglycerin ointment is not intended for immediate relief or 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, especially when higher dosages of the ointment are used. Headache may be treated with concomitant administration of mild analgesics. If headache is unresponsive to such treatment, the dose of nitroglycerin ointment should be reduced or the use of the product discontinued.
Less frequently, postural hypotension, an increase in heart rate, faintness, flushing, dizziness, nausea and dermatitis have been reported.
Symptoms And Treatment Of Overdose: Symptoms: Symptoms of overdosage are primarily related to vasodilation, including cutaneous flushing, headache, nausea, dizziness and hypotension. Methemoglobinemia is also possible.
Treatment: No specific antidote is available. Ointment should be wiped off immediately, followed by symptomatic and supportive treatment.
Dosage And Administration: Angina Pectoris: Ointment may be applied every 3 to 8 hours if necessary, but one application at bedtime frequently suffices for the entire night. The usual dose is 2.5 to 5 cm as squeezed from the tube. The optimal dose is determined by starting with an application of 1.25 cm and increasing the dose by 1.25 cm at a time until side effects (usually headache) occur or satisfactory response is obtained. Some patients may require as much as 10 to 12.5 cm, and/or application every 4 hours.
Nitroglycerin ointment is effective in the control of angina pectoris regardless of the site of application on the skin. Therefore, any convenient skin area may be used, but many patients prefer the chest because anginal pain originates in this area.
Method of application: Using Appli-ruler: In applying the ointment, the specially designed Appli-ruler (supplied in each package) is placed printed-side down, and the necessary amount of ointment is squeezed from the tube onto the applicator. Then, the applicator is placed with the ointment-side down onto the desired area of the skin, usually the chest (although other areas can be used). The ointment is spread over at least 50´75 mm area in a thin uniform layer using the Appli-ruler that serves the dual purpose of measuring the amount of ointment and preventing absorption of the ointment through the fingers while it is being applied. The ointment should be covered with the Appli-ruler paper, plastic kitchen wrap or other suitable material. This can be held in place with adhesive or transparent tape.
Availability And Storage: Each tube of ointment contains: 2% nitroglycerin. Nonmedicinal ingredients: lactose, lanolin, petrolatum and purified water. Tubes of 30 and 60 g. Keep tube tightly closed and store at room temperature (15 to 30°C).
NITROL® Rhône-Poulenc Rorer Nitroglycerin Antianginal – Vasodilator