People taking nitrates like nitroglycerin Nitrostat or isosorbide mononitrate Imdur should not take PDE5 inhibitors, as doing so could result in a dangerous drop in blood pressure. More serious side effects may include a drop in blood pressure or an erection that lasts longer than four hours. Which Is More Effective? Viagra is always taken as needed, usually an hour before having sex. Oral ED medicines might not work or might be dangerous if you also take any of the following: Nitrate medicines.Welcome to provides prescription and OTC drugs through a leading pharmacy in Canada and other international pharmacies. We provide thousands of prescription drugs and over-the-counter products at savings of up to 80 percent or more.  · You’ll typically take Viagra about 1 hour before sex. You can take the drug 30 minutes to 4 hours before you anticipate sexual activity. Based on how well you respond to this dosage and any side. 1 day ago · The Viagra Triangle is a district in Chicago’s Gold Coast neighborhood in the city’s north side. The triangle is formed by State and Rush streets coming together with Bellevue Street being its.