The usage of an organic nitrate such as nitroglycerin along with Viagra (sildenafil citrate) is most dangerous. A new drug prescribed for erectile dysfunction, can be a deadly mix. According to the FDA, 69 Viagra users in the United States died between late March and July 1998. Of these, 12 had also taken nitroglycerin or another nitrate medication. Such a mix is contraindicated because it can cause a large, sudden drop in systemic BP.
Although short-acting nitrates may be routinely prescribed for angina, Viagra's manufacturer, Pfizer, warns ED personnel not to administer them to patients taking Viagra. Other drugs to avoid include isosorbide mononitrate, isosorbide dinitrate, pentaerythritol tetranitrate, and erythrityl tetranitrate. Inhaling nitrates such as amyl nitrate/nitrite, or "poppers" for entertaining purpose almost creates similar risks.