Stendra avanafil : This is an as-needed medication taken 30 minutes before sex and can last up to six hours. In some cases, ED can cause a strain on relationships and impact self-esteem. Cialis stays in your system for up to 36 hours, and you can take it daily. Emling S. They require a prescription for any controlled substance and have a licensed pharmacist to answer questions rather than support staff. Cialis reaches its maximum effectiveness two hours after you take it. Those who don’t feel comfortable discussing ED with an in-person provider or lack time to visit a doctor’s office may find online ED prescriptions beneficial.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 (Cialis). Cialis (tadalafil) and Viagra are both used for erectile dysfunction, but there are a couple of distinctions between the two. Unlike Viagra, low-dose tadalafil can be taken on a daily basis, allowing for more spontaneity. What’s more, a single dose of tadalafil lasts up to 36 hours, whereas a dose of Viagra only lasts for around four hours. 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.