Viagra (generic name: sildenafil) is a medication primarily used to treat erectile dysfunction (ED) in men. Viagra is typically available in oral tablet form, with common doses ranging from 25mg to 100mg. The usual recommended starting dose is 50mg, taken approximately 30 minutes to 1 hour before sexual activity. The effects can last for 4 to 6 hours, although it is not an aphrodisiac and requires sexual arousal to work.