Nitroglycerin (NTG) is a quick-acting medication used to treat angina, which is chest discomfort caused by the heart muscle not receiving enough oxygen-rich blood. Angina often feels like pressure, squeezing, or heaviness. NTG works by relaxing and widening the blood vessels, which improves blood flow to the heart and also reduces the heart’s workload. Knowing the correct administration protocol and when to call emergency medical services (EMS) is important, as chest pain can also signal a heart attack.
Proper Administration Techniques
When angina begins, sit down immediately before taking the medication. NTG is a potent vasodilator that can cause a sudden drop in blood pressure, leading to dizziness or fainting. Sitting helps prevent falls or injury. The medication is typically administered sublingually (under the tongue) as a small tablet or spray. The tablet must dissolve completely without chewing or swallowing, allowing rapid absorption into the bloodstream. Store NTG in its original, dark glass container away from heat and moisture, and regularly check the expiration date.
The Critical Dosing Protocol and EMS Activation
The standard protocol begins at the first sign of chest discomfort. Place one dose (tablet or spray) under the tongue and wait five minutes. During this time, the medication should begin to take effect, and the chest pain may subside completely. If the chest pain is not relieved or worsens after the first five-minute interval, call 911 or local EMS immediately. After calling for emergency help, you may then take a second dose of nitroglycerin. The third dose should only be taken if the pain persists another five minutes after the second dose. If the chest pain has not resolved after a total of three doses over a 15-minute period, it is considered a medical emergency requiring professional intervention. The primary focus must remain on the rapid activation of EMS.
Essential Safety Warnings and Drug Interactions
NTG use is dangerous if you have certain conditions or are taking specific medications, due to the risk of severe hypotension (low blood pressure). Avoid taking NTG if your systolic blood pressure is already below 100 mmHg. Since NTG’s primary action is vasodilation, combining it with low baseline blood pressure can cause dizziness, fainting, or cardiovascular collapse.
A dangerous interaction occurs with phosphodiesterase type 5 (PDE5) inhibitors, such as sildenafil (Viagra) or tadalafil (Cialis), which are used for erectile dysfunction (ED). Both NTG and PDE5 inhibitors cause blood vessel relaxation, and their combined effect can dramatically and fatally lower blood pressure. If you have taken sildenafil or vardenafil within the last 24 hours, or tadalafil within the last 48 hours, you must not take nitroglycerin.
A common side effect of nitroglycerin is a headache, which occurs because the widening of blood vessels affects those in the head as well. While a mild headache can be a sign that the medication is working, report any severe or persistent headache to your healthcare provider. Alcohol consumption should also be avoided, as it worsens the blood pressure-lowering effects of nitroglycerin.
Actions While Awaiting Emergency Services
Once EMS has been called, remain calm and avoid physical exertion, which increases the heart’s demand for oxygen. Stay seated or lie down to minimize injury risk from a sudden drop in blood pressure. Do not attempt to drive yourself to the hospital. If you are not allergic to aspirin, the 911 operator may instruct you to chew a standard dose (162 to 325 mg). Aspirin helps to inhibit platelet aggregation, essentially making the blood less sticky, which can slow the formation of a clot in a coronary artery. Ensure the nitroglycerin bottle is easily accessible for emergency personnel.