Nitroglycerin

Chest Pain (Angina)

Nitroglycerin is most commonly prescribed to manage angina, which is chest pain that occurs when the heart muscle does not receive enough blood flow. It is used in two main ways:

• Treatment of acute attacks: Quick-acting forms, such as sublingual tablets or oral sprays, are used to stop a chest pain attack that has already started.
• Prevention of attacks: Long-acting forms, including extended-release capsules, skin patches, and ointments, are used daily to reduce the frequency of chest pain episodes.

In some cases, fast-acting nitroglycerin is used shortly before physical exercise or stressful events to prevent chest pain from occurring during those activities.

Anal Fissures

A specific rectal formulation of nitroglycerin is used to treat pain associated with chronic anal fissures, which are small tears in the lining of the anus. This medication helps by relaxing the muscles and reducing pressure in the area to alleviate discomfort.

Mechanism of Action

Nitroglycerin belongs to a class of medications called vasodilators. It works by relaxing the smooth muscles that make up the walls of the blood vessels.

Improving Blood Flow

When the blood vessels relax and widen, blood can flow more easily through the body. This process provides several benefits:

• Increased oxygen: Widening the arteries that supply the heart allows more oxygen-rich blood to reach the heart muscle.
• Reduced workload: Because the vessels are wider, the heart does not have to pump as hard to move blood, which reduces the heart's demand for oxygen.

Other Uses

When used for specific conditions like anal fissures, nitroglycerin works by relaxing the internal anal sphincter muscle. This relaxation reduces pressure in the area and improves local blood flow, which helps the tissue heal and reduces pain.

Common Side Effects

Many people experience mild side effects when taking nitroglycerin. These often improve as your body gets used to the medicine. Common side effects include:

• Headache, which may be severe
• Dizziness or lightheadedness
• Nausea or vomiting
• Flushing (redness or warmth in the face, neck, or chest)
• Weakness
• Blurred vision

Serious Side Effects

Contact a healthcare provider immediately if you experience any of the following serious symptoms:

• Fainting or feeling very faint
• Fast, slow, or pounding heartbeat
• Chest pain that gets worse
• Signs of an allergic reaction, such as rash, hives, itching, or swelling of the face, lips, or throat
• Difficulty breathing or swallowing
• Bluish color of the skin, lips, or fingernails
• Extreme tiredness or lack of energy
• Fever

If you are using the rectal ointment, you may experience rectal pain or burning. Topical or transdermal forms may cause skin irritation or redness where the medication was applied.

Drug Interactions

Nitroglycerin must not be used by individuals taking phosphodiesterase-5 (PDE5) inhibitors, such as sildenafil, tadalafil, or vardenafil. Combining these medications can cause a sudden and life-threatening drop in blood pressure. It should also not be used with riociguat, a medication used for pulmonary arterial hypertension.

Low Blood Pressure and Dizziness

This medication can cause a significant drop in blood pressure, leading to dizziness, lightheadedness, or fainting. These effects are more likely to occur when moving from a sitting or lying position to standing (orthostatic hypotension). Alcohol consumption can increase these blood pressure-lowering effects and should be avoided or limited.

Nitrate Tolerance

The body can develop a tolerance to nitroglycerin if it is used continuously, meaning the medication may become less effective over time. To help prevent this, healthcare providers often recommend a nitrate-free interval of several hours each day.

Headaches

Severe headaches are a very common side effect of nitroglycerin therapy. These headaches are often a sign that the medication is working and may decrease in frequency or intensity as the body adjusts to the treatment.

Medical Conditions and Precautions

Caution is necessary for individuals with certain health conditions, including:

• Severe anemia
• Increased pressure within the skull (intracranial pressure)
• Recent heart attack or heart failure
• Severe dehydration or low blood volume
• Hypertrophic cardiomyopathy

Administration and Safety

Sublingual tablets or sprays must not be swallowed, as they are designed to be absorbed through the lining of the mouth. For those using transdermal patches, some products contain aluminum or other metals in the backing; these must be removed before undergoing an MRI or cardioversion to prevent skin burns. Rectal nitroglycerin may cause dizziness, and individuals should avoid driving or operating machinery until they know how the medication affects them.

Pregnancy

There are no adequate and well-controlled studies on the use of nitroglycerin in pregnant women. While animal reproduction studies have generally not shown evidence of harm to the fetus, animal data does not always predict how a human will respond to the medication. Because the potential risks are not fully understood, nitroglycerin should be used during pregnancy only if a healthcare provider determines that the potential benefit justifies the potential risk to the fetus.

Breastfeeding

It is not known whether nitroglycerin is excreted in human breast milk. Because many drugs are passed through breast milk, caution is recommended when nitroglycerin is administered to someone who is nursing. Patients should discuss the potential risks and benefits with their doctor or healthcare professional before using this medication while breastfeeding.

Sublingual and Buccal Forms

These fast-acting forms are used to treat an active angina attack or are taken just before activities that may cause chest pain:

• Sublingual tablets: Placed under the tongue to dissolve.
• Sublingual powder: Packets of powder placed under the tongue.
• Sublingual spray: Sprayed onto or under the tongue.

Oral Forms

Oral nitroglycerin is used for the long-term prevention of angina and will not work fast enough to treat a sudden attack:

• Extended-release capsules: Swallowed whole to provide a steady release of medication over time.

Transdermal and Topical Forms

These forms are applied to the skin for the continuous prevention of chest pain:

• Transdermal patches: Adhesive patches that deliver medication through the skin over a period of hours.
• Topical ointment: Applied to the skin using a dose-measuring applicator.

Rectal Form

• Rectal ointment: A specific formulation used to treat pain caused by chronic anal fissures.

Injectable Form

• Intravenous (IV) solution: Administered by healthcare providers in a hospital setting for acute heart conditions or during surgical procedures.

FDA Approval and Indications

Nitroglycerin is approved by the U.S. Food and Drug Administration (FDA) for several clinical uses, which vary based on the method of administration:

• Sublingual and Lingual formulations: These fast-acting forms, such as tablets or sprays, are approved for the acute relief of a sudden angina attack or for the prevention of angina before activities that might trigger chest pain.
• Transdermal and Extended-release formulations: Patches and extended-release capsules are approved for the long-term prevention of angina pectoris due to coronary artery disease. These forms are not intended for the immediate relief of an ongoing attack.
• Rectal formulation: Nitroglycerin rectal ointment is FDA-approved for the treatment of moderate to severe pain associated with chronic anal fissures.

Regulatory Status

Nitroglycerin is available only by prescription. While it is a long-standing medication in cardiovascular care, it does not currently carry a Boxed Warning, which is the FDA's most serious type of warning. There are no Risk Evaluation and Mitigation Strategies (REMS) programs required for its use.

Patients should be aware that different brands and generic versions of nitroglycerin may have specific storage requirements or expiration timelines mandated by the FDA to ensure the medication remains stable and effective.

How to Use Sublingual Nitroglycerin

Sublingual nitroglycerin comes as tablets or a spray that is placed under the tongue. It is used to treat an active angina attack or to prevent chest pain before activities that might cause it, such as exercise or cold weather exposure.

• Administration: Place the tablet or spray under the tongue or in the pouch of the cheek. Do not swallow, chew, or crush the medication, as it needs to be absorbed through the lining of the mouth to work quickly.
• Timing: Use the medication at the first sign of chest pain or pressure. Sit down before taking it, as it may cause dizziness or lightheadedness.
• Emergency Steps: If chest pain does not improve or gets worse after the first dose, seek emergency medical care immediately. You may be instructed to take up to three doses, five minutes apart, while waiting for help.

Storage and Handling

Proper storage is essential for sublingual tablets to remain effective:

• Keep tablets in their original dark glass container.
• Close the cap tightly after every use.
• Do not store other medications in the same bottle.
• Avoid exposing the medication to heat, light, or moisture.