If you have heart disease (eg angina pectoris "chest pain") and you are being treated with medicines that contain nitrates, or substances which release nitric oxide (eg molsidomine, nitroglycerin or similar substances), you should in any case take sildenafil (Viagra). Take Viagra at the same time that these drugs may enhance their effect dangerously and cause a voltage drop or circulatory collapse. If you take a drug like this, talk to your doctor. If you're not sure, ask your doctor or pharmacist. For the above reasons (risk of dangerous interaction with Viagra), you must not take any "poppers" sold illegally (which contain amyl nitrite as the active ingredient). If you take Viagra, taking medicines containing nitrates or substances which release nitric oxide (eg molsidomine, nitroglycerin or similar substances) is strictly prohibited. This also applies in case of sudden onset of heart problems (such as chest pain, angina pectoris). This type of medical emergency requires that you (or your partner / close) do know all the people who treat you that you have taken Viagra. Anyway, you should immediately contact your doctor. Alone can decide what to do. Do not take Viagra if you have ever had an allergic reaction to Viagra or one of its components listed under "Composition". An allergic reaction can manifest as a rash, itching, congestion of the face, swollen lips or shortness of breath. In this case, let your doctor know. Viagra should not be administered to children or adolescents under 18 years.