Your healthcare provider will discuss which dose is right for you. All PDE5 inhibitors, including Viagra and Cialis, require a valid prescription regardless of the pharmacy or provider. Viagra Choosing the right ED pill can be intimidating. They are PDE5 inhibitors that allow for increased blood flow to the penis, leading to more frequent and harder erections. Erectile dysfunction can be caused by a variety of factors , including age, cardiovascular problems, diabetes, and other conditions that affect nerve function or blood flow.Viagra, Cialis, Levitra, and Stendra are oral medications used to treat erectile dysfunction (ED). You may also know them by their generic names: sildenafil (Viagra) tadalafil . You need a prescription to get Cialis, which you can acquire through your doctor or telehealth sources. Online ordering can be a great alternative if you prefer the . Differences Oral medications are a simple and effective way to treat erectile dysfunction (ED). The most common erectile dysfunction pill is Viagra, and the next most common is .