How Nitro Bid Works as a Vasodilator
Nitro Bid, a topical ointment containing the active ingredient nitroglycerin, belongs to a class of medications called nitrates. Its primary pharmacological action is to relax the smooth muscles within the walls of blood vessels, a process known as vasodilation. By relaxing and widening these blood vessels, nitroglycerin increases blood flow and reduces the workload on the heart, which in turn helps alleviate or prevent certain symptoms.
When applied topically, the nitroglycerin is absorbed through the skin, releasing nitric oxide within the body. This nitric oxide triggers a cascade of cellular events that ultimately lead to the relaxation of blood vessel walls. This effect is utilized for two main therapeutic purposes: the prevention of angina and the treatment of anal fissures.
Use for Angina (Chest Pain) Prophylaxis
One of the most common applications for Nitro Bid is the long-term prevention of angina pectoris, or chest pain, in individuals with coronary artery disease. Angina occurs when the heart muscle does not receive enough oxygen-rich blood, often due to narrowed coronary arteries. Nitro Bid helps in several ways:
- Relaxes blood vessels: It widens the coronary arteries, allowing more blood and oxygen to reach the heart muscle.
- Reduces cardiac workload: By dilating other peripheral veins, it decreases the amount of blood returning to the heart (preload), reducing the strain on the heart muscle.
It is crucial to note that Nitro Bid is not a fast-acting treatment for an acute angina attack. For immediate relief, faster-acting forms of nitroglycerin, such as sublingual tablets or sprays, are used. To prevent tolerance to the medication, a nitrate-free interval of typically 10–12 hours per day is required.
Administration for Angina
For angina prophylaxis, Nitro Bid is typically applied to a non-hairy skin area, such as the chest or back, using a special applicator. The administration often involves applying a measured amount of ointment a couple of times a day. It is important to spread the ointment lightly and not rub it in, as rubbing can alter absorption. After applying, the applicator paper is often taped in place, and the area can be covered with plastic wrap to prevent staining clothes.
Use for Anal Fissures
Another distinct use for nitroglycerin ointment, specifically the brand Rectiv, is the treatment of moderate to severe pain associated with chronic anal fissures. An anal fissure is a small tear or crack in the lining of the anus, often caused by hard stools or straining during bowel movements. By relaxing the anal sphincter muscle, the ointment can:
- Reduce pressure: It lowers the resting pressure in the anal canal, which helps decrease pain and muscle spasms.
- Improve blood flow: Increased blood flow to the area promotes healing of the fissure.
Administration for Anal Fissures
For this purpose, a lower-strength, compounded nitroglycerin ointment may be prescribed. It is typically applied directly to the anal canal, usually using a finger covered with a protective layer like plastic wrap. The administration is usually a measured amount, applied at regular intervals for a specified period. Proper hygiene and administration techniques are crucial to maximize effectiveness and minimize side effects.
Contraindications and Side Effects
Nitro Bid, like all medications, has potential side effects and contraindications. Patients should be aware of these before starting treatment.
Major Contraindications
- Use with PDE-5 inhibitors: The most significant contraindication is the concomitant use with erectile dysfunction drugs like sildenafil (Viagra) and tadalafil (Cialis). This combination can cause a severe and dangerous drop in blood pressure.
- Increased intracranial pressure: Patients with head injuries or cerebral hemorrhages should not use nitroglycerin, as it can increase pressure within the skull.
- Severe anemia: Patients with severe anemia should also avoid it.
Common Side Effects
- Headaches: This is the most frequently reported side effect and may indicate that the medication is working properly.
- Dizziness and lightheadedness: These can occur, especially when standing up too quickly (orthostatic hypotension).
- Flushing: A feeling of warmth, redness, or tingling sensation.
Comparison of Nitroglycerin Ointments for Angina vs. Anal Fissures
| Feature | Angina Prophylaxis | Anal Fissure Treatment |
|---|---|---|
| Application Site | Non-hairy skin areas like chest, back. | Rectal canal. |
| Mechanism of Action | Vasodilation reduces heart workload and increases coronary blood flow. | Relaxes anal sphincter, reducing pressure and promoting blood flow. |
| Typical Strength | Standard concentrations, such as 2%. | Often compounded lower strengths, such as 0.2% or 0.4%. |
| Frequency | Typically twice daily, with a nitrate-free interval. | Typically at regular intervals for a specified duration. |
| Purpose | Prevents future attacks of chest pain. | Treats existing pain and promotes healing. |
| Tolerance | Avoided by including a daily nitrate-free interval. | Less of a concern, but can still occur. |
Conclusion
Nitro Bid ointment is a prescription medication with two distinct uses, each requiring specific application methods and administration instructions. For patients with coronary artery disease, it acts as a preventative measure against angina by improving blood flow and reducing heart strain. Alternatively, a compounded nitroglycerin ointment can be used to treat the pain and promote the healing of anal fissures. Given its potent vasodilatory effects, careful adherence to medical instructions and a thorough understanding of its contraindications, particularly with certain other medications, is essential for safe and effective treatment. Consult with a healthcare provider to ensure proper usage and to monitor for any side effects.
For more detailed information on nitroglycerin, you can visit the National Institutes of Health website.
