Testosterone Gel Fails to Boost Viagra's Effects, Boston University School of Medicine Study

Men who have erectile dysfunction and low testosterone may get no extra benefit from adding the hormone to their Viagra prescription, a new study suggests. The first-choice treatments for erectile dysfunction are drugs called PDE5 inhibitors, which include sildenafil (Viagra), vardenafil (Levitra) and tadalafil (Cialis). They work by helping the smooth muscles of the penis to relax, which increases blood flow.