It might work longer if you have mild to moderate erectile dysfunction. Sildenafil Viagra. These medicines all work well for ED. They’re often the first line of treatment for trouble getting or keeping an erection, called erectile dysfunction ED. Sildenafil is in a class of medications called phosphodiesterase PDE inhibitors.Sildenafil (Viagra) is a phosphodiesterase-5 (PDE-5) inhibitor. PDE-5 is a protein in your body that breaks down the molecules that normally cause an erection. When it blocks . Description and Brand Names Drug information provided by: Merative, Micromedex ® US Brand Name Revatio Viagra Descriptions Sildenafil is used to treat men who have . Generic Viagra (sildenafil) is an alternative to the branded Viagra drug that can be used for treating erectile dysfunction (ED). It’s now sold by many manufacturers, including online.