Fildena 120 mg is typically taken 30 minutes to 1 hour before sexual activity. It starts working within 30 minutes to an hour, with effects lasting up to 4 hours. Fildena 120 mg should not be taken with certain medications, particularly those containing nitrates (often used to treat chest pain), as this combination can cause a sudden and serious drop in blood pressure. It's important to inform your doctor about all medications you are taking, including over-the-counter and herbal supplements.