Sexual function data were also recorded by patients in a daily diary. Percentage of Patients Reporting an Improvement in Erections. The pattern of responses was similar for the other principal question, the ability to achieve an erection sufficient for intercourse. Two of the questions from the IIEF served as primary study endpoints; categorical responses were elicited to questions about 1 the ability to achieve erections sufficient for sexual intercourse and 2 the maintenance of erections after penetration. The possible categorical responses to these questions were 0 no attempted intercourse, 1 never or almost never, 2 a few times, 3 sometimes, 4 most times, and 5 almost always or always. About sildenafil Viagra Sildenafil is a medicine used to treat erection problems erectile dysfunction. It launched on December 11, Viagra (sildenafil) is an oral drug that is used for treating impotence (or erectile disfunction, ED, the inability to attain or maintain a penile erection). It is in a class of drugs called phosphodiesterase inhibitors (PDE-5 inhibitors) that also includes. tadalafil (),; vardenafil (Levitra, Staxyn ODT), and; avanafil ().; It has been estimated that impotence . In addition to Viagra, REX MD also offers brand-name Cialis and generic Cialis (tadalafil). Both Viagra and sildenafil are available in mg, mg, and mg doses.  · See a doctor if you notice any of the following uncommon or rare side effects when you take Teva sildenafil: sharp or burning chest pain that gets worse over time. pain in your bladder. stomach.