Fildena is effective in improving erectile function for many men with ED. It is known for its fast onset of action and relatively long duration compared to some other ED medications. The onset of action for Fildena can vary depending on the strength and individual factors. Generally, Fildena starts working within 30 minutes to an hour after ingestion. The effects can last for up to 4 to 6 hours, providing a sufficient window of opportunity for sexual activity.