Both Cialis and Viagra work in this way. Other conditions that may disqualify you from an ED prescription include a history of stroke, kidney or liver disease, cancer, diabetes, or a bleeding disorder. You can see an in-person provider or speak with a doctor virtually. Now, the Drug Enforcement Agency DEA has proposed new rules that will require an in-person visit for anything more than a day supply of controlled substances to be filled by an online pharmacy. There is also the option to take Cialis as needed.Buying Viagra Online: The 5 Best Online Viagra Sources of On this page We include products we think are useful for our readers. If you buy through links on this page, we may earn a small. 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.