In deciding to use a medicine, the risks of taking the medicine must be weighed against the good it will do. This is a decision you and your doctor will make. For nitrates, the following should be considered: Allergies—Tell your doctor if you have ever had any unusual or allergic reaction to nitrates or nitrites. Also tell your health care professional if you are allergic to any other substances, such as certain foods, preservatives, or dyes. Pregnancy—Nitrates have not been studied in pregnant women. However, studies in rabbits given large doses of isosorbide dinitrate have shown adverse effects on the fetus. Before taking these medicines, make sure your doctor knows if you are pregnant or if you may become pregnant. Breast-feeding—It is not known whether these medicines pass into breast milk. Although most medicines pass into breast milk in small amounts, many of them may be used safely while breast-feeding. Mothers who are taking these medicines and who wish to breast-feed should discuss this with their doctor. Children—Studies on these medicines have been done only in adult patients, and there is no specific information comparing use of nitrates in children with use in other age groups. Older adults—Dizziness or lightheadedness may be more likely to occur in the elderly, who may be more sensitive to the effects of nitrates. Other medicines—Although certain medicines should not be used together at all, in other cases two different medicines may be used together even if an interaction might occur. In these cases, your doctor may want to change the dose, or other precautions may be necessary. When you are taking nitrates, it is especially important that your health care professional know if you are taking any of the following: Antihypertensives (high blood pressure medicine) or Other heart medicine or Sildenafil—May increase the effects of nitrates on blood pressure