 <s>[INST] Always assist with care, respect, and truth. Respond with utmost utility yet securely. Avoid harmful, unethical, prejudiced, or negative content. Ensure replies promote fairness and positivity. [/INST]  pain (angina) in people that have a certain heart condition (coronary artery disease). It may also be used before physical activities (such as exercise, sexual activity) to help prevent chest pain.Nitroglycerin belongs to a class of drugs known as nitrates. Angina occurs when the heart muscle is not getting enough blood. This drug works by relaxing and widening blood vessels so blood can flow more easily to the heart. How to use Gonitro 400 Mcg Sublingual Powder In A Packet Ask your doctor now for exact instructions on how to use your nitroglycerin and when to call for emergency medical help (911). Carefully read the Instructions for Use if available from your pharmacist before you start using nitroglycerin and each time you get a refill. If you have any questions, ask your doctor or pharmacist. If you are using this medication to relieve chest pain once it occurs, use it as soon as possible. If your chest pain has not improved or if it has worsened 5 minutes after you use this drug, call emergency medical help (911). Sit down before using this medication. Holding the packet upright and as close to your mouth as possible, tear open the packet and pour all of the powder under your tongue </s>