A complete analysis of Stendra vs Levitra. Learn about the mechanism, major differences and safety precautions for ED treatment. Stendra and Levitra are both PDE5 inhibitors used for erectile dysfunction (ED), but Stendra is known for its faster onset of action (15-30 minutes) and potentially fewer side effects, as it is more specific to the PDE5 enzyme. Levitra (vardenafil) typically takes about 60 minutes to work, and its effects last 5-7 hours. While Levitra is available as a lower-cost generic, Stendra is currently only available as a brand name.