Like all medications, Tadagra 20 mg may cause side effects in some people. Common side effects may include headache, indigestion, back pain, muscle aches, flushing, stuffy or runny nose, and dizziness. Serious side effects are rare but may include sudden vision loss, sudden hearing loss, chest pain, and priapism (a prolonged erection lasting more than four hours). If you experience any severe or persistent side effects while taking Tadagra, seek medical attention promptly.