The dosage of fildena double 200 mg helps men with erectile dysfunction get an erection. Aim for about an hour before bedtime. Take the prescription. Alcohol use reduces the effectiveness of this drug, making it dangerous to take. After 4 to 6 hours, the body starts to feel the effects of this tablet. Do not use this drug if you are a woman or child. The body feels the effects of this tablet for four to six hours. This medication poses a risk to minors and women.