Sildenafil Citrate (Generic Viagra®) Erectile Dysfunction, (Impotence), is the persistent inability to achieve and maintain an erection sufficient to complete sexual intercourse.

Sildenafil is taken orally as needed between four hours and one-half hour before sexual activity (about one hour before is most effective). Take only as directed, usually once daily as needed. Sildenafil works along with sexual stimulation to help achieve an erection.