SIDE EFFECTS: Headache may occur, but usually lasts a short time after each dose. With continued use of this medication, some people may not be bothered as much by the headaches. Your doctor may recommend treating headaches with a nonprescription pain reliever (such as acetaminophen). Nitroglycerin can also cause a drop in your blood pressure, which can lead to dizziness and lightheadedness. To reduce the risk of dizziness and lightheadedness, get up slowly when rising from a sitting or lying position. If any of these effects persist or worsen, tell your doctor or pharmacist promptly. Remember that your doctor has prescribed this medication because he or she has judged that the benefit to you is greater than the risk of side effects. Many people using this medication do not have serious side effects. A very serious allergic reaction to this drug is rare. However, get medical help right away if you notice any symptoms of a serious allergic reaction, including: rash, itching/swelling (especially of the face/tongue/throat), severe dizziness, trouble breathing. This is not a complete list of possible side effects. If you notice other effects not listed above, contact your doctor or pharmacist. In the US - Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088 or at www.fda.gov/medwatch. In Canada - Call your doctor for medical advice about side effects. You may report side effects to Health Canada at 1-866-234-2345.

PRECAUTIONS: Before using this medication, tell your doctor or pharmacist if you are allergic to nitroglycerin; or to nitrates, nitrites, or isosorbide; or if you have any other allergies. This product may contain inactive ingredients, which can cause allergic reactions or other problems. Talk to your pharmacist for more details. Before using this medication, tell your doctor or pharmacist your medical history, especially of: anemia, low blood pressure, loss of too much body water (dehydration), increased pressure inside your head (such as due to head/brain injury), heart/blood vessel problems (such as heart failure, recent heart attack). This drug may make you dizzy. Alcohol or marijuana can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely. Limit alcoholic beverages because they can also cause a drop in your blood pressure. Talk to your doctor if you are using marijuana. Before having surgery, tell your doctor or dentist about all the products you use (including prescription drugs, nonprescription drugs, and herbal products). Older adults may be more sensitive to the side effects of this medication, especially dizziness and lightheadedness. During pregnancy, this medication should be used only when clearly needed. Discuss the risks and benefits with your doctor. It is unknown if this medication passes into breast milk. Consult your doctor before breast-feeding.

DRUG INTERACTIONS: Drug interactions may change how your medications work or increase your risk for serious side effects. This document does not contain all possible drug interactions. Keep a list of all the products you use (including prescription/nonprescription drugs and herbal products) and share it with your doctor and pharmacist. Do not start, stop, or change the dosage of any medicines without your doctor's approval. Some products that may interact with this drug include: drugs to treat erectile dysfunction-ED or pulmonary hypertension (such as sildenafil, tadalafil), riociguat.

OVERDOSE: This medicine may be harmful if swallowed. If someone has overdosed and has serious symptoms such as passing out or trouble breathing, call 911. Otherwise, call a poison control center right away. US residents can call their local poison control center at 1-800-222-1222. Canada residents can call a provincial poison control center. Symptoms of overdose may include: pale/gray/blue colored skin/lips/nails, severe headache, fainting, shortness of breath, fast heartbeat, confusion, unusual tiredness.