nitroglycerin

Nitroglycerin belongs to a class of drugs called nitrates. Nitroglycerin is used for the treatment and prevention of angina caused by coronary artery disease. Nitroglycerin also is used intravenously to treat congestive heart failure associated with heart attack and high blood pressure during surgery.

Sublingual nitroglycerin and nitroglycerin spray are used to treat acute anginal attacks. Transdermal nitroglycerin, nitroglycerin ointment and capsules do not act rapidly enough to be used for acute anginal attacks.

Nitroglycerin in a nitrate. Other nitrates include isosorbide dinitrate (Isordil) and isosorbide mononitrate (Imdur, Ismo, Monoket).

• Blood returning from the body in the veins must be pumped by the heart through the lungs and into the arteries against the high pressure in the arteries.
• In order to accomplish this work, the heart's muscle must produce and use energy ("fuel").
• The production of energy requires oxygen. Angina pectoris (angina) or "heart pain" is due to an inadequate flow of blood (and oxygen) to the muscle of the heart.
• It is believed that all nitrates, including nitroglycerin, have their effects by dilating (widening) the arteries and veins throughout the body. In patients with angina, nitroglycerin preferentially dilates blood vessels that supply the areas of the heart where there is not enough blood flow and oxygen thereby delivering oxygen to the heart muscle that needs it most. In addition, blood is redistributed to the body within the widened veins, and this reduces the amount of blood returning to the heart that needs to be pumped. Therefore, the heart has less work to do and requires less blood and oxygen. Dilation of the arteries also lowers the pressure in the arteries against which the heart must pump. As a consequence, the heart works even less and requires less blood and oxygen.

Synthesized in 1846, nitroglycerin was first used to treat anginal attacks in 1879. It was granted FDA approval in 1938.

Common side effects include:

• headache and
• lightneadedness

Aspirin, acetaminophen (Tylenol and others), or ibuprofen (Advil, Motrin, Nuprin, and others) may be used to relieve the pain.

Other side effects include:

• Nausea
• Vomiting
• Fainting
• Blurred vision

More serious side effects include flushing of the head and neck can occur with nitroglycerin therapy as can an increase in heart rate or palpitations. This can be associated with a drop in blood pressure which can be accompanied by dizziness or weakness. To reduce the risk of low blood pressure, patients often are told to sit or lie down during and immediately after taking nitroglycerin.

• For the treatment of acute angina attacks or for acute prevention (for example, immediately before encountering situations likely to bring on an anginal attack), one tablet is allowed to dissolve under the tongue or between the cheek and gums, or one spray is given of the lingual spray. Sublingual, spray, and buccal nitroglycerin are rapidly absorbed from the lining of the mouth for immediate effects. This may be repeated every 5 minutes as needed. If angina is not relieved after a total of 3 doses, the patient should be taken to a hospital or a doctor should be contacted. If the lingual spray is used, the canister of the spray should not be shaken prior to use, and it should be sprayed onto or under the tongue and then the mouth closed.
• For prevention of angina, ointment may be applied using special dose-measuring application papers provided with the ointment. The usual dose is 1/2 to 2 inches applied every 4-6 hours. The appropriate amount of ointment is squeezed as a thin layer onto the paper, and the paper is used to spread the ointment onto a non-hairy area of the skin. The ointment should not be allowed to come into contact with the hands where it can be absorbed.
• Transdermal patches also are used for prevention. The usual dose is 0.2-0.8 mg/hr applied for 12 hours and then removed. An additional 12 hours should be allowed before applying the next patch because a 12-hour nitroglycerin-free period reduces the occurrence of tolerance to the effects (reduced effectiveness) of nitroglycerin. Patches may be applied to any hairless site but should not be applied to areas with cuts or calluses which can alter absorption. Firm pressure should be used over the patch to ensure contact with the skin. The patch should not be cut or trimmed. Patches are waterproof and should not be affected by showering or bathing.
• Capsules of long-acting nitroglycerin also are used for prevention. The usual dose is 2.5-9 mg administered 2 to 3 times per day 1 to 2 hours after a meal. Capsules should be swallowed whole and not chewed.

Since nitroglycerin can cause hypotension (low blood pressure), other medications which also cause hypotension may produce severe hypotension. Such drugs might include medicines used to:

• treat high blood pressure,
• some antidepressants;
• some anti-psychotics,
• quinidine (Quinaglute, Quinidex),
• procainamide (Pronestyl, Procan-SR, Procanbid),
• benzodiazepines such as diazepam (Valium), or
• opiates, for example, morphine.

Since alcohol also may intensify the blood pressure lowering effect of nitroglycerin, patients receiving nitroglycerin should be advised to drink alcoholic beverages with caution.

Sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra), and avanafil (Stendra) exaggerate the blood pressure lowering effects of nitroglycerin and may cause excessive blood pressure reduction. Patients taking nitrates should not take sildenafil, tadalafil, vardenafil, or avanafil.

Ergot alkaloids, for example, ergotamine with caffeine-rectal (Cafergot, Migergot), and sumatriptan (Imitrex) can oppose the vasodilatory actions of nitroglycerin and may cause angina. A similar effect can occur with ephedrine and the decongestants pseudoephedrine (Sudafed) and propanolamine which is contained in many drugs used for treating the symptoms of colds.

Nitroglycerin has not been adequately studied in pregnant women.

It is not known if nitroglycerin is secreted in breast milk.

What preparations of nitroglycerin are available?

• Tablets: 0.3, 0.4, 0.6 mg;
• Capsules: 2.5, 6.5, 9 mg; Spray: 0.4 mg/spray;
• Transdermal Patch: 0.1, 0.2, 0.3, 0.4, 0.6, 0.8 mg/hour;
• Ointment: 2%;
• Infusion Solution: 25, 50, 100 mg/250 ml
• Injectable solution: 5 mg/ml.

How should I keep nitroglycerin stored?

All formulations should be kept at room temperature, 15 C to 30 C (59 F to 86 F). The sublingual tablets are especially susceptible to moisture. They should NOT be kept in bathrooms or kitchens because of the greater moisture in these rooms. Care should be taken to replace the sublingual tablets every six months.