Valif 20 mg commonly contains vardenafil 20 mg, a PDE5 inhibitor used to treat erectile dysfunction (ED) in adult men. It works by increasing blood flow to the penis during sexual stimulation, helping an erection develop and remain firm. It does not increase sexual desire and requires sexual stimulation to work. Vardenafil generally begins working within 30–60 minutes, although individual responses vary. The effect usually lasts for several hours. A high-fat meal may delay absorption.