You should call a doctor about Fildena CT 50mg side effects if you experience any severe or persistent reactions. Immediate medical attention is necessary if you notice symptoms such as chest pain, prolonged erection (lasting more than 4 hours), sudden vision or hearing loss, or allergic reactions like swelling, difficulty breathing, or rash. If you experience dizziness, lightheadedness, or fainting, especially after standing up, it could indicate low blood pressure and requires medical advice. Any unusual side effects like nausea, headache, or muscle pain should also be reported to your doctor for further guidance on managing the medication.