- After your doctor confirms that you have erectile dysfunction, he will likely suggest treatment options such as penile injections, vacuum pumps, and impotence tablets. Many men now prefer Fildena (Viagra) for impotence. The FDA has approved Viagra and it is proven safe and effective. It is best to take the Fildena CT tablet 60 minutes before you start sexual activity. The medicine's effects last for approximately 4 hours. Fildena can be used to stimulate sexual activity. It will provide a firm, prolonged erection that is essential for having sexual intercourse.