Fildena 120 mg is a higher-strength formulation compared with many commonly prescribed sildenafil doses. Because of its higher amount of active ingredient, it should be used only under the guidance of a healthcare professional. Taking a higher dose without medical advice may increase the risk of side effects. Possible side effects of Fildena 120 mg include headache, flushing, dizziness, nasal congestion, indigestion, and temporary changes in vision. Rare but serious reactions may include chest pain, fainting, sudden vision or hearing changes, or a prolonged erection that requires immediate medical attention.