It lasts 4 to 5 hours, or longer if you have mild to moderate ED. Never purchase ED medications from a site or service that doesn’t require a prescription and medical documentation. It might work longer if you have mild to moderate erectile dysfunction. Other conditions that may disqualify you from an ED prescription include a history of stroke, kidney or liver disease, cancer, diabetes, or a bleeding disorder. People with heart conditions should never take ED medications without consulting a doctor. This medicine works best when you take it on an empty stomach an hour before sex. These PDE5 inhibitors may cause headache, flushing, drop in blood pressure, or other adverse effects.Medical Consultation Required: Yes Medications Prescribed: Viagra, Cialis, sildenafil, tadalafil Generic offered: Yes Why We Chose It. Do not take Viagra if you are also using a nitrate drug for chest pain or heart problems, including nitroglycerin, isosorbide dinitrate, isosorbide mononitrate, and some . $ retail Save 91% $ Get free savings Most popular Safeway $ retail Save 94% $ Get free savings Low price Walgreens $ retail Save 94% $ Get free .