Zudena 100 mg is a medication that contains udenafil, which is used to treat erectile dysfunction (ED). It works by increasing blood flow to the penis during sexual stimulation, helping to achieve and maintain an erection. Zudena 100 mg tablet is typically taken about 15 to 30 minutes before sexual activity. Sexual arousal is necessary for it to be effective. Common side effects may include headaches, flushing, nasal congestion, dizziness, and gastrointestinal discomfort. More severe side effects are rare but should be reported to a healthcare professional immediately.