Nitro-Bid is a prescription ointment containing 2% nitroglycerin, applied to the skin to prevent angina (chest pain) in people with coronary artery disease. It works by relaxing and widening blood vessels, which reduces the heart’s workload and improves blood flow to the heart muscle. Nitro-Bid is not designed to stop chest pain that’s already happening. It’s a preventive treatment, meant to reduce how often angina episodes occur.
How Nitro-Bid Works
Coronary artery disease narrows the blood vessels that feed the heart. When the heart needs more oxygen during physical activity or stress, those narrowed vessels can’t deliver enough blood, causing the squeezing or pressure sensation of angina. Nitroglycerin, the active ingredient in Nitro-Bid, relaxes the smooth muscle in blood vessel walls. This widens both the arteries supplying the heart and the veins returning blood to it, lowering the overall demand on the heart.
Because the ointment is absorbed through the skin, the nitroglycerin enters the bloodstream gradually. This slow, steady delivery is what makes it useful for prevention rather than for stopping an acute episode. For sudden chest pain, faster-acting forms like sublingual tablets (dissolved under the tongue) are used instead.
How It’s Measured and Applied
Nitro-Bid uses an unusual dosing system: inches of ointment squeezed from the tube. Each inch (about 2.5 cm) contains roughly 15 mg of nitroglycerin. Doses tested in clinical trials ranged from half an inch (7.5 mg) to 2 inches (30 mg). A typical starting regimen is half an inch applied twice daily, once in the morning and again about six hours later.
The ointment comes with dose-measuring paper. You squeeze the prescribed length onto the paper, then place the paper ointment-side down on a clean, dry, hairless area of skin, usually the chest, upper arm, or upper back. You don’t rub it in. The paper stays in place, often secured with medical tape, allowing the nitroglycerin to absorb steadily. Rotating the application site each time helps prevent skin irritation.
One important precaution: avoid touching the ointment with your bare hands. Nitroglycerin absorbs through any skin it contacts, so caregivers helping with application should wear gloves to prevent accidentally absorbing the medication themselves.
The Nitrate-Free Window
One quirk of all nitroglycerin products is that the body develops tolerance to them surprisingly fast. If the medication is present in your bloodstream around the clock, it gradually stops working. To prevent this, treatment schedules build in a daily “nitrate-free interval” of 8 to 12 hours, typically overnight. That’s why Nitro-Bid is applied in the morning and again in the early afternoon rather than spread evenly across 24 hours. Removing any remaining ointment before bed gives the body time to reset its sensitivity to the drug.
Common Side Effects
Headache is the most frequent side effect, and it’s directly related to how the drug works. Nitroglycerin dilates blood vessels throughout the body, including those in the head. For many people, these headaches lessen after the first week or two of use as the body adjusts.
Dizziness and flushing are also common. Because nitroglycerin lowers blood pressure, standing up quickly can cause a drop that makes you feel lightheaded or faint. Standing up slowly from a seated or lying position helps reduce this. These effects tend to be most noticeable when you first start the medication or after a dose increase.
More concerning symptoms like persistent dizziness, blurred vision, or feeling like you might pass out suggest blood pressure may have dropped too low. These warrant a prompt call to your care team.
A Critical Drug Interaction
Nitro-Bid has one interaction that is genuinely dangerous: combining it with medications used for erectile dysfunction. Drugs like sildenafil (Viagra), vardenafil (Levitra), and tadalafil (Cialis) also dilate blood vessels. Taken together with any form of nitroglycerin, they can cause a severe, potentially life-threatening drop in blood pressure.
The American Heart Association considers all nitrates contraindicated within 24 hours of sildenafil or vardenafil, and within 48 hours of tadalafil (which stays active in the body longer). This applies in both directions. If you’re using Nitro-Bid, you should not take these medications. The same goes for recreational “poppers” (amyl nitrite), which are chemically similar to nitroglycerin and carry the same risk.
What’s in the Ointment
The formulation is straightforward: 2% nitroglycerin (20 mg per gram of ointment) in a base of lanolin, white petrolatum, purified water, and lactose. The petrolatum base is what gives it its greasy, ointment-like consistency and helps control the rate of absorption through the skin. Because of the greasy texture, many people find it easiest to apply before getting dressed and to wear an older shirt during the hours it’s on.