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. Avanafil Stendra. Vardenafil usually works for 4 to 5 hours. Medicines that you take by mouth are called oral medicines. Insurance: If you plan to use insurance, make sure the online provider accepts it.Sildenafil (Viagra). This medicine works best when you take it on an empty stomach an hour before sex. The body takes longer to absorb it after a high-fat meal or . Viagra Coupons, Prices, and Savings Card Generic Names: Sildenafil Citrate Brand Names: Revatio Sildenafil is used to treat male sexual function problems (impotence or erectile . CHOOSE BRAND-NAME VIAGRA. The original little blue pill prescribed by doctors for over 20 years. Clinically proven to treat men with erectile dysfunction (ED) Ongoing .