Thee prescription drugs, Vardenafil (Levitra), tadalafil (Cialis) and sildenafil (Viagra) called phosphodiesterase type 5 (PDE-5) inhibitors, are regarded as the first-line treatment for most cases of erectile dysfunction. The medication is taken orally and helps men to get and keep an erection with sexual stimulation. They cannot help men to have an erection if they are not sexually stimulated. One of the benefits of this form of treatment is that it is taken before sexual intercourse and therefore doesn't interrupt the sex act. The amount of time before a couple is ready for sexual intercourse when taking these Viagra , Cialis tablets varies according to which medication is prescribed.