Cialis is most commonly used to treat erectile dysfunction and impotence, which is when a man struggles to maintain an erection or cannot get erect at all. It's also sometimes prescribed for an enlarged prostate.
Tadalafil is the active ingredient of Cialis. It improves blood flow to the penis so that a man can get an erection for sexual activity.
Depending on how your doctor prescribes the medication, you might take it as needed before sex or every day. If you take it as needed, the effects may last up to 36 hours.
Levitra is used to treat erectile dysfunction, which is a man's inability to maintain an erection. It works by relaxing muscles in the penis, allowing more blood to flow to it.
The active ingredient in Levitra is vardenafil. The medication was first made available in 2003, and in the United States, you can only obtain it with a prescription.
Levitra is taken on an as-needed basis, about one hour before you want to have sex. Alcohol and grapefruit should be avoided when taking this medication as they can produce severe side effects.