The active ingredient in Fildena 100 is sildenafil citrate, which is a drug used to treat erectile dysfunction (ED) in men. It's also important to note that taking Fildena 100mg with a high-fat meal may lessen its effects. Fildena 100 should be taken at least 30 minutes before engaging in sexual activity. Take this medication half an hour before sexual activity. Follow your doctor's advice when taking this medication. This medication has a 4- to 6-hour half-life.