Never purchase ED medications from a site or service that doesn’t require a prescription and medical documentation. Your primary care doctor should always know what medications you’re taking, including ED pills prescribed by another provider. Stendra avanafil : This is an as-needed medication taken 30 minutes before sex and can last up to six hours. 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. It’s best to check your chosen provider’s site for more information. Side effects of Sildenafil and Tadalafil will differ from person to person.How we vet brands and products Erectile dysfunction medications, including Viagra and Cialis, help the muscles in the penis relax so you can get and maintain an . Was this helpful? How does Cialis work? Cialis works by increasing blood flow to the penis to help a person get and maintain an erection. It also blocks the PDE5 .