25. Competition Manufacturer Pfizer Eli Lilly Bayer First Available to Public March, 1998 November, 2003 August, 2003 Drug (Active Ingredient) Name Sildenafil Tadalafil Vardenafil Duration of Effectiveness About 4 hours Up to 36 hours About 5 hours Nickname "The Little Blue Pill," "Vitamin V" "The Weekend Pill" Levitra