Nitroglycerin (NTG) is a medication used to rapidly treat acute chest pain, known as angina, which signals reduced blood flow to the heart muscle. As a potent vasodilator, it quickly relaxes and widens blood vessels, including the coronary arteries, improving oxygen supply to the heart and reducing its workload. Understanding the precise protocol is important because angina can signal a serious, time-sensitive event, such as a heart attack. Correct use alleviates symptoms and serves as a diagnostic step in determining the condition’s severity.
The Standard Nitroglycerin Protocol for Angina
When chest pain begins, immediately cease physical activity, and sit or lie down comfortably. This reduces the heart’s demand for oxygen, which may resolve symptoms on its own. The sitting or lying position is also important because nitroglycerin causes blood pressure to drop rapidly, and standing could lead to dizziness or fainting.
Once settled, administer a single dose of nitroglycerin—either a sublingual tablet or a spray—at the first sign of symptoms. Sublingual administration allows the medication to be absorbed quickly into the bloodstream, bypassing the digestive system for a faster onset of action, typically within one to five minutes. The tablet must dissolve completely without being chewed, swallowed, or washed down with water, which prevents proper absorption.
After taking the first dose, wait a full five minutes to assess the medication’s effect. The standard protocol allows the dose to be repeated every five minutes, up to a maximum of three doses in a fifteen-minute period, but only if the pain is mild and decreasing. The decision to call for emergency medical services is often made earlier, as persistent or worsening pain indicates a medical emergency.
The Critical Threshold: When to Activate Emergency Services
The most important instruction is to call 911 immediately if the chest pain is not completely relieved or if it worsens within five minutes of taking the first dose. Waiting longer than this five-minute threshold is dangerous, as the heart muscle is likely continuing to be deprived of oxygen. Pain that persists after the initial dose suggests a potentially life-threatening event, such as an ongoing heart attack, requiring advanced medical intervention.
Delaying the call to take a second or third dose wastes time during which irreversible heart muscle damage may occur. Nitroglycerin serves as a diagnostic indicator as much as a treatment in this scenario. If the pain is due to a simple spasm or temporary imbalance, it should resolve quickly; if it does not, the patient must assume a serious cause is present.
The five-minute rule is a clear trigger designed to prompt a rapid response from emergency medical services (EMS). Even if the pain is only partially relieved, or if the patient is unsure of the severity, the safest course of action is to call 911. Professional medical personnel are best equipped to assess the situation and provide advanced cardiac care that cannot be provided at home. Do not drive yourself or have a family member drive you to the emergency room, as the medical support provided by EMS en route can be lifesaving.
Immediate Actions While Waiting for Help Arrive
Once 911 is called, remain on the phone with the emergency dispatcher for instructions and monitoring. While waiting for EMS, the patient must remain seated or lie down to minimize the risk of a dangerous drop in blood pressure, which nitroglycerin can exacerbate. If the patient feels faint or dizzy, lying down with the feet slightly elevated helps promote blood flow back to the brain.
If instructed by the dispatcher, a second dose of nitroglycerin should be administered five minutes after the first dose. The patient should also unlock the front door to ensure paramedics can enter without delay, as seconds count in a cardiac emergency. Gathering a list of current medications and medical conditions is helpful, as this information will be immediately relevant to the arriving EMS team.
If possible, direct someone to wait outside to flag down the ambulance and guide them to the patient’s location. The priority remains staying calm and conserving energy, as unnecessary movement increases the heart’s workload.
Understanding Nitroglycerin Safety Information
Beyond emergency use, safety considerations for handling and storing nitroglycerin ensure its effectiveness. The medication is highly sensitive and must be stored in its original amber glass vial with the cap tightly secured to protect it from light, heat, and moisture. Avoid placing cotton or other medications inside the vial, as this affects the stability and potency of the tablets.
Nitroglycerin tablets lose strength over time, so it is recommended to replace the supply six months after the bottle has been opened, regardless of the printed expiration date. Patients should be aware of common side effects, such as a throbbing headache, flushing of the face, and lightheadedness. These are signs the drug is working by causing blood vessels to dilate. Headaches can often be managed with over-the-counter pain relievers, but severe headaches should be reported to a healthcare provider.
A serious safety concern involves contraindications with phosphodiesterase type 5 (PDE5) inhibitors, used to treat erectile dysfunction (e.g., sildenafil, tadalafil). Combining nitroglycerin with these drugs can cause a profound and life-threatening drop in blood pressure due to their synergistic vasodilatory effect. Patients must not take nitroglycerin if they have taken sildenafil (Viagra) within the last 24 hours or tadalafil (Cialis) within the last 48 hours.