Zudena 100 mg tablet (sildenafil) is a medication used to treat erectile dysfunction. After taking it, the drug is absorbed into your bloodstream and reaches peak levels within a few hours. The body metabolizes sildenafil primarily in the liver through enzymes, and it is then excreted through the kidneys. The elimination half-life of sildenafil is about 4 hours, which means it takes around that time for the concentration of the drug in your blood to reduce by half. Generally, it takes about 5 half-lives for a drug to be eliminated from your system, so sildenafil should be mostly cleared from your body within 24 to 30 hours.