Sildenafil (Viagra)
Sildenafil (Viagra) Viagra (sildenafil) is a prescription medication used to treat erectile dysfunction. Headache, flushing, and upset stomach are common Viagra side effects. These effects are usually mild and often resolve on their own. While rare, Viagra can cause an erection that lasts longer than 4 hours (priapism). Sildenafil (Viagra). This medicine works best when