Nitroglycerin ointment is a topical vasodilator that works by relaxing and widening blood vessels. When applied to the skin, the medication is absorbed and begins to work on the smooth muscles of the blood vessels. This relaxation increases blood flow to the specific area of application and can decrease the overall workload on the heart.
Medical Uses for Nitroglycerin Ointment
The most common medical use for nitroglycerin ointment today is for the treatment of pain associated with chronic anal fissures. An anal fissure is a small, painful tear in the tissue lining the anus. These tears can cause sharp pain and bleeding, particularly during bowel movements, and are often slow to heal due to muscle spasms in the internal anal sphincter, which reduce blood supply to the area.
When applied rectally, the ointment is absorbed and acts directly on the internal anal sphincter muscle, causing it to relax. This relaxation lowers the pressure within the anus, which not only alleviates pain but also significantly improves blood flow to the site of the fissure. This treatment is considered when more conservative measures have not provided relief.
Historically, nitroglycerin ointment was also a treatment for angina, or chest pain, caused by reduced blood flow to the heart. By applying the ointment to the skin on the chest, the vasodilation effect would reduce the heart’s workload and alleviate the pain. This application has become less common for angina, with treatments like sublingual tablets and transdermal patches now being more standard due to their more precise and consistent dosing.
Proper Application and Dosage
Before and after each use, it is important to wash your hands thoroughly. The medication comes with marked paper applicators designed to measure the precise dose prescribed by a healthcare provider. Use these applicators for measurement rather than estimating with a finger to ensure accuracy and avoid direct contact with the ointment.
To apply, the measured dose is placed on a finger, which may be covered with plastic wrap or a finger cot, and then gently applied just inside the anal canal as directed. The ointment should not be inserted deeply into the rectum. The goal is for the medication to make contact with the tissue around the anal opening to reach the internal sphincter muscle.
A common dosage frequency is every 12 hours. This schedule helps maintain a steady level of the medication in the body, ensuring the anal sphincter remains relaxed to promote continuous healing. If a dose is missed, it should be applied as soon as remembered, unless it is almost time for the next scheduled dose. In that case, the missed dose should be skipped to avoid applying a double amount.
Potential Side Effects
The vasodilating properties of nitroglycerin ointment can also lead to side effects, with the most frequently reported being a headache. This occurs because the medication is absorbed into the bloodstream and dilates blood vessels throughout the body, including those in the head. This can lead to a throbbing headache, which is often a sign the medication is working, and these headaches diminish in severity as the body acclimates to the treatment.
Other common side effects include dizziness, lightheadedness, and flushing of the skin. These symptoms are often related to a temporary drop in blood pressure and are more likely to occur when changing positions quickly, such as standing up from a sitting or lying position.
While most side effects are manageable, some require immediate medical attention. These include a severe or persistent headache that does not improve, fainting, blurred vision, or an unusually fast or slow heartbeat. Such symptoms could indicate a more serious reaction to the medication, and a healthcare provider should be consulted.
Important Precautions and Drug Interactions
Patients with pre-existing conditions such as severe anemia, increased intracranial pressure from a head injury, or glaucoma should use this medication with caution, as it could worsen these conditions. Individuals who are pregnant or breastfeeding should consult their doctor to weigh the potential benefits against any risks.
A primary safety concern involves interactions with other drugs. Nitroglycerin ointment must never be used concurrently with medications for erectile dysfunction (ED), such as sildenafil, tadalafil, and vardenafil, or with certain drugs used for pulmonary hypertension. This combination can trigger a sudden, severe, and potentially fatal drop in blood pressure. It is also advisable to limit alcohol consumption, as it can amplify the blood pressure-lowering effects of the ointment and increase feelings of dizziness or lightheadedness.