Erectile dysfunction can stem from many causes and can range from complete inability to achieve an erection at all, to inability to maintain an erection long enough to have satisfactory intercourse.
Many men have a problem with erectile function at some time in their lives.
The treatments available before the approval of Viagra were penile implants, various mechanical methods of producing and maintaining an erection, the injection of a drug into the penis itself, and the recently approved Muse, a tablet that is inserted into the tip of the penis. Although both the injection and Muse produce good erections in a large percentage of men, both techniques require doing something slightly unpleasant and interrupting the intimacy of the moment. Viagra, in contrast, is taken about one hour before one anticipates having sex. It enhances and prolongs the chemical changes in the penis that come with sexual arousal and that induce the erection. It will not induce an erection unless the man becomes sexually stimulated.