When taken at the correct time and paired with sexual stimulation, the erection lasts long enough for successful intercourse. Cialis tadalafil : This ED medication works with the same principle as Viagra, but lasts up to 36 hours. You can report an adverse event either online, by regular mail or by fax, using the contact information at the bottom of this page. Stendra avanafil : This is an as-needed medication taken 30 minutes before sex and can last up to six hours. A small number of patients taking Cialis also reported abnormal vision. Those with a history of blood pressure or heart issues, hormonal imbalances, mental health issues, and diabetes should consult their doctor before trying PDE5 inhibitors.Cialis (tadalafil) is an expensive drug used to treat erection problems in men. It may also be used to treat the enlargement of the prostate gland. This drug is slightly more popular than comparable drugs. It is available in both brand and generic versions. 1. What is Cialis used to treat? Cialis is approved for the treatment of men who experience difficulty having and maintaining an erection (impotence). 2. How does Cialis work? Cialis works. How Tadalafil (Cialis) works. Tadalafil (Cialis) is a phosphodiesterase-5 enzyme (PDE-5) inhibitor. It works by blocking PDE This is a protein in your body that breaks down the molecules that normally cause an erection.