Nitroglycerin ointment is a prescription topical medication used to manage the pain associated with chronic anal fissures. An anal fissure is a small tear in the thin tissue lining the anus, often causing significant discomfort. The ointment is a nitrate vasodilator that influences blood vessels and muscle tone in the localized area. It is typically prescribed when conservative treatments, such as increased fiber intake and sitz baths, have failed to promote healing. The application aims to reduce the pressure that prevents the fissure from healing.
How the Ointment Works
The ointment’s therapeutic action begins immediately upon absorption by the skin around the anal canal. Once absorbed, nitroglycerin converts into nitric oxide (NO) within the tissue. NO is a signaling molecule that plays a crucial role in relaxing smooth muscles throughout the body. This localized NO production targets the internal anal sphincter muscle, which is often in spasm with chronic fissures.
Relaxation of this involuntary muscle ring reduces the resting pressure within the anal canal. Reducing this high pressure is crucial because it prevents blood flow, hindering the natural healing process. This relaxation creates a “chemical sphincterotomy” effect, which is the medication’s primary goal. The resulting vasodilation increases blood flow to the compromised tissue, delivering necessary oxygen and nutrients to promote tissue repair and healing.
Practical Application Instructions
The typical dose involves measuring a specific amount of the 0.4% ointment, often a line about one inch long, delivering approximately 1.5 milligrams of nitroglycerin. Always use the provided measuring guide on the packaging to ensure the correct dosage. This amount is generally applied twice daily, usually every 12 hours, for the period determined by a healthcare provider.
A protective barrier, such as a disposable surgical glove, finger cot, or plastic wrap, must cover the finger used for application. This barrier prevents accidental absorption through the skin of the finger, which could increase the risk of systemic side effects. Gently squeeze the ointment onto the covered finger, matching the length of the dosing line.
The preferred method involves gently inserting the covered finger into the anal canal, only as far as the first joint, and lightly smearing the ointment around the inner sides. If the pain is too severe for internal application, the ointment may be applied directly to the skin outside the anus. After application, safely discard the finger covering and thoroughly wash the hands to remove any residual medication.
Managing Common Adverse Effects
The most frequently reported side effect is headache, which can be severe. This occurs because systemic absorption causes vasodilation in the blood vessels of the head, increasing blood flow and pressure, resulting in a throbbing headache. Headaches often lessen in intensity with continued use as the body develops tolerance.
Patients should not alter their prescribed application schedule to avoid headaches, as this reduces treatment effectiveness. Taking an over-the-counter analgesic, such as acetaminophen, about 30 minutes before application can help mitigate the discomfort.
Another common adverse effect is dizziness or lightheadedness, stemming from a temporary drop in blood pressure known as orthostatic hypotension. This occurs when changing position too quickly, such as moving from sitting or lying to standing. To manage this, individuals should rise slowly from a seated or reclined position following application.
Serious Safety Warnings and Drug Interactions
A significant safety warning involves a severe, life-threatening interaction with a class of medications called Phosphodiesterase Type 5 (PDE5) inhibitors. These include drugs used for erectile dysfunction, such as sildenafil, tadalafil, and vardenafil. Combining nitroglycerin and a PDE5 inhibitor causes an additive effect of vasodilation throughout the body.
This interaction can lead to an uncontrolled drop in blood pressure, potentially causing fainting, cardiovascular collapse, or death. Nitroglycerin ointment must not be used within a few days of taking any PDE5 inhibitor. Patients must inform their healthcare provider about all current medications to avoid this serious interaction.
The ointment is also contraindicated for individuals with certain pre-existing conditions, including severe anemia or increased intracranial pressure. These conditions can be exacerbated by the medication’s systemic effects. Seek immediate medical attention if you experience extreme dizziness, fainting, blurred vision, or signs of a severe allergic reaction after applying the ointment.